Updated on 2022/10/10

写真a

 
KUSANO, Kanya
 
Organization
Institute for Space-Earth Environmental Research Division for Integrated Studies Professor
Graduate School
Graduate School of Science
Title
Professor
Contact information
メールアドレス

Degree 1

  1. Doctor of Science ( 1987.4   Hiroshima University ) 

Research Interests 30

  1. Space weather & space climate

  2. Celestial dynamo

  3. Solar flare

  4. 超水滴

  5. 宇宙気候

  6. 宇宙天気

  7. 宇宙プラズマ

  8. 太陽フレア

  9. 太陽コロナ

  10. ダイナモ

  11. シミュレーション

  12. エアロゾル

  13. super-droplet

  14. Space Weather

  15. Space Plasmas

  16. Space Climate

  17. Solar Flares

  18. Solar Corona

  19. Simulations

  20. Self-Organization

  21. Science of Hierarchical Structure

  22. Nonlineaer Magnetohydrodynamics

  23. Dynamos

  24. cloud

  25. aerosol

  26. 非線形電磁流体力学

  27. 階層構造の科学

  28. 自己組織化

  29. 核融合

Research Areas 8

  1. Others / Others  / Upper Atmospheric Physics

  2. Others / Others  / Plasma Physics

  3. Others / Others  / Astrophysics

  4. Energy Engineering / Fundamental plasma

  5. Natural Science / Mathematical physics and fundamental theory of condensed matter physics

  6. Natural Science / Space and planetary sciences

  7. Natural Science / Astronomy

  8. Natural Science / Theoretical studies related to particle-, nuclear-, cosmic ray and astro-physics

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Current Research Project and SDGs 3

  1. Holistic Modeling of Solar-Terrestrial System

  2. Solar flare onset mechanism, and the origin of sunspot activity

  3. solar influence on terrestrial environment

Research History 27

  1. Nagoya University   Institute for Space-Earth Environmental Research   Director

    2017.4

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    Country:Japan

  2. Nagoya University   Institute for Space-Earth Environmental Research (ISEE)   Director

    2017.4

  3. Nagoya University   Institute for Space-Earth Environmental Research   Director in General

    2017.4 - 2020.3

  4. Nagoya University   Institute for Space-Earth Environmental Research   Professor

    2015.10

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    Country:Japan

  5. Nagoya University   Institute for Space-Earth Environmental Research (ISEE)   Professor

    2015.10

  6. Nagoya University   Institute for Space-Earth Environmental Research (ISEE)   Deputy Director

    2015.10 - 2017.3

  7. Nagoya University   STEL   Deputy Director

    2012.4 - 2015.9

  8. Nagoya University   Solar-Terrestrial Environment Laboratory   Professor

    2009.7 - 2015.9

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    Country:Japan

  9. Nagoya University   STEL   Professor

    2009.7 - 2015.9

  10. Japan Agency for Marine-Earth Science and Technology

    2009.4 - 2009.6

  11. 独立行政法人海洋研究開発機構地球内部ダイナミクス領域地球内部ダイナミクス基盤研究プログラム階層システム研究チーム・チームリーダー

    2009.4

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    Country:Japan

  12. 名古屋大学太陽地球環境研究所客員教授

    2008.5 - 2009.3

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    Country:Japan

  13. 東京工業大学大学院理工学研究科客員教授

    2008.4

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    Country:Japan

  14. 明治大学大学院理工学研究科客員教授

    2008.4

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    Country:Japan

  15. 広島大学大学院先端物質科学研究科客員教授

    2005.12 - 2008.3

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    Country:Japan

  16. 独立行政法人海洋研究開発機構地球シミュレータセンター連結階層シミュレーション研究開発プログラム・プログラムディレクター

    2005.11 - 2009.3

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    Country:Japan

  17. Japan Agency for Marine-Earth Science and Technology

    2005.11 - 2009.3

  18. 独立行政法人海洋研究開発機構地球シミュレータセンター連結階層シミュレーション研究開発プログラムアルゴリズム研究グループ・グループリーダー

    2004.9 - 2005.10

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    Country:Japan

  19. Japan Agency for Marine-Earth Science and Technology

    2004.9 - 2005.10

  20. 広島大学大学院先端物質科学研究科助教授

    1998.4 - 2004.8

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    Country:Japan

  21. Hiroshima University   Graduate School of Advanced Sciences of Matter

    1998.4 - 2004.3

  22. 広島大学理学部助教授

    1996.4 - 1998.3

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    Country:Japan

  23. Hiroshima University   Faculty of Science

    1996.4 - 1998.3

  24. 広島大学理学部助手

    1987.6 - 1996.3

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    Country:Japan

  25. Hiroshima University   Faculty of Science

    1987.5 - 1996.3

  26. 日本学術振興会特別研究員

    1986.4 - 1987.5

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    Country:Japan

  27. Japan Society for Promotion of Science

    1986.4 - 1987.4

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Education 4

  1. Hiroshima University   Graduate School, Division of Natural Science   Department of Materials Science

    1984.4 - 1987.3

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    Country: Japan

  2. Hiroshima University   Graduate School of Science

    1982.4 - 1987.3

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    Country: Japan

  3. Hiroshima University   Graduate School, Division of Natural Science   Department of Materials Science

    1982.4 - 1984.3

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    Country: Japan

  4. Hokkaido University   Faculty of Science   Department of Physics

    1978.4 - 1982.3

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    Country: Japan

Professional Memberships 7

  1. The Physical Society of Japan

    2006.4 - 2010.3

  2. The Astronomical Society of Japan

  3. Society of Geomagnetism and Earth, Planetary and Space Sciences

  4. The Japan Society of Plasma Science and Nuclear Fusion Research

  5. International Astronomical Union   Organizing Committee Member of Division II Commission 10 Solar Activity

    2009.10 - 2011.10

  6. American Astronomical Society

  7. The American Geophysical Union

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Awards 3

  1. 令和4年度科学技術分野の文部科学大臣表彰科学技術賞(研究部門)

    2022.4   文部科学省  

    巨大太陽フレアの精密予測と発生機構に関する研究

  2. 西宮湯川記念賞

    1998  

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    Country:Japan

  3. 井上研究奨励賞

    1987  

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    Country:Japan

 

Papers 185

  1. A physics-based method that can predict imminent large solar flares Reviewed International journal

    Kanya Kusano, Tomoya Iju, Yumi Bamba, Satoshi Inoue

    Science   Vol. 369 ( 6503 ) page: 587 - 591   2020.7

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    Authorship:Lead author   Language:Japanese   Publishing type:Research paper (scientific journal)   Publisher:American Association for the Advancement of Science (AAAS)  

    Solar flares are highly energetic events in the Sun’s corona that affect Earth’s space weather. The mechanism that drives the onset of solar flares is unknown, hampering efforts to forecast them, which mostly rely on empirical methods. We present the κ-scheme, a physics-based model to predict large solar flares through a critical condition of magnetohydrodynamic instability, triggered by magnetic reconnection. Analysis of the largest (X-class) flares from 2008 to 2019 (during solar cycle 24) shows that the κ-scheme predicts most imminent large solar flares, with a small number of exceptions for confined flares. We conclude that magnetic twist flux density, close to a magnetic polarity inversion line on the solar surface, determines when and where solar flares may occur and how large they can be.

    DOI: 10.1126/science.aaz2511

    Web of Science

  2. Impact of subsurface convective flows on the formation of sunspot magnetic field and energy build-up

    Takafumi Kaneko, Hideyuki Hotta, Shin Toriumi, Kanya Kusano

    Monthly Notices of the Royal Astronomical Society     2022.9

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    Language:English   Publishing type:Research paper (scientific journal)   Publisher:Oxford University Press (OUP)  

    Abstarct

    Strong solar flares occur in δ-spots characterized by the opposite-polarity magnetic fluxes in a single penumbra. Sunspot formation via flux emergence from the convection zone to the photosphere can be strongly affected by convective turbulent flows. It has not yet been shown how crucial convective flows are for the formation of δ-spots. The aim of this study is to reveal the impact of convective flows in the convection zone on the formation and evolution of sunspot magnetic fields. We simulated the emergence and transport of magnetic flux tubes in the convection zone using radiative magnetohydrodynamics code R2D2. We carried out 93 simulations by allocating the twisted flux tubes to different positions in the convection zone. As a result, both δ-type and β-type magnetic distributions were reproduced only by the differences in the convective flows surrounding the flux tubes. The δ-spots were formed by the collision of positive and negative magnetic fluxes on the photosphere. The unipolar and bipolar rotations of the δ-spots were driven by magnetic twist and writhe, transporting magnetic helicity from the convection zone to the corona. We detected a strong correlation between the distribution of the nonpotential magnetic field in the photosphere and the position of the downflow plume in the convection zone. The correlation could be detected 20–30 h before the flux emergence. The results suggest that high free energy regions in the photosphere can be predicted even before the magnetic flux appears in the photosphere by detecting the downflow profile in the convection zone.

    DOI: 10.1093/mnras/stac2635

  3. Modeling the Transport and Deposition of Be-10 Produced by the Strongest Solar Proton Event During the Holocene

    Spiegl T. C., Yoden S., Langematz U., Sato T., Chhin R., Noda S., Miyake F., Kusano K., Schaar K., Kunze M.

    JOURNAL OF GEOPHYSICAL RESEARCH-ATMOSPHERES   Vol. 127 ( 13 )   2022.7

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    Language:Japanese   Publishing type:Research paper (scientific journal)  

    DOI: 10.1029/2021JD035658

    Web of Science

  4. Generation of Solar-like Differential Rotation

    Hotta H., Kusano K., Shimada R.

    ASTROPHYSICAL JOURNAL   Vol. 933 ( 2 )   2022.7

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    Language:Japanese   Publishing type:Research paper (scientific journal)  

    DOI: 10.3847/1538-4357/ac7395

    Web of Science

  5. Solar differential rotation reproduced with high-resolution simulation

    H. Hotta, K. Kusano

    Nature Astronomy   Vol. 5 ( 11 ) page: 1100 - 1102   2021.11

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    Language:Japanese   Publishing type:Research paper (scientific journal)   Publisher:Springer Science and Business Media LLC  

    DOI: 10.1038/s41550-021-01459-0

    Web of Science

    Other Link: https://www.nature.com/articles/s41550-021-01459-0

  6. Special issue "Solar-terrestrial environment prediction: toward the synergy of science and forecasting operation of space weather and space climate"

    Kusano Kanya, Ishii Mamoru, Berger Tomas, Miyoshi Yoshizumi, Yoden Shigeo, Liu Huixin, Onsager Terry, Ichimoto Kiyoshi

    EARTH PLANETS AND SPACE   Vol. 73 ( 1 )   2021.10

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    Language:Japanese   Publishing type:Research paper (scientific journal)  

    DOI: 10.1186/s40623-021-01530-0

    Web of Science

  7. PSTEP: project for solar-terrestrial environment prediction

    Kanya Kusano, Kiyoshi Ichimoto, Mamoru Ishii, Yoshizumi Miyoshi, Shigeo Yoden, Hideharu Akiyoshi, Ayumi Asai, Yusuke Ebihara, Hitoshi Fujiwara, Tada-Nori Goto, Yoichiro Hanaoka, Hisashi Hayakawa, Keisuke Hosokawa, Hideyuki Hotta, Kornyanat Hozumi, Shinsuke Imada, Kazumasa Iwai, Toshihiko Iyemori, Hidekatsu Jin, Ryuho Kataoka, Yuto Katoh, Takashi Kikuchi, Yuki Kubo, Satoshi Kurita, Haruhisa Matsumoto, Takefumi Mitani, Hiroko Miyahara, Yasunobu Miyoshi, Tsutomu Nagatsuma, Aoi Nakamizo, Satoko Nakamura, Hiroyuki Nakata, Naoto Nishizuka, Yuichi Otsuka, Shinji Saito, Susumu Saito, Takashi Sakurai, Tatsuhiko Sato, Toshifumi Shimizu, Hiroyuki Shinagawa, Kazuo Shiokawa, Daikou Shiota, Takeshi Takashima, Chihiro Tao, Shin Toriumi, Satoru Ueno, Kyoko Watanabe, Shinichi Watari, Seiji Yashiro, Kohei Yoshida, Akimasa Yoshikawa

    EARTH PLANETS AND SPACE   Vol. 73 ( 1 )   2021.8

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    Language:Japanese   Publishing type:Research paper (scientific journal)   Publisher:SPRINGER  

    Although solar activity may significantly impact the global environment and socioeconomic systems, the mechanisms for solar eruptions and the subsequent processes have not yet been fully understood. Thus, modern society supported by advanced information systems is at risk from severe space weather disturbances. Project for solar-terrestrial environment prediction (PSTEP) was launched to improve this situation through synergy between basic science research and operational forecast. The PSTEP is a nationwide research collaboration in Japan and was conducted from April 2015 to March 2020, supported by a Grant-in-Aid for Scientific Research on Innovative Areas from the Ministry of Education, Culture, Sports, Science and Technology of Japan. By this project, we sought to answer the fundamental questions concerning the solar-terrestrial environment and aimed to build a next-generation space weather forecast system to prepare for severe space weather disasters. The PSTEP consists of four research groups and proposal-based research units. It has made a significant progress in space weather research and operational forecasts, publishing over 500 refereed journal papers and organizing four international symposiums, various workshops and seminars, and summer school for graduate students at Rikubetsu in 2017. This paper is a summary report of the PSTEP and describes the major research achievements it produced.

    DOI: 10.1186/s40623-021-01486-1

    Web of Science

  8. Eruptivity in Solar Flares: The Challenges of Magnetic Flux Ropes

    Lin Pei Hsuan, Kusano Kanya, Leka K. D.

    ASTROPHYSICAL JOURNAL   Vol. 913 ( 2 )   2021.6

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    Language:Japanese   Publishing type:Research paper (scientific journal)  

    DOI: 10.3847/1538-4357/abf3c1

    Web of Science

  9. Space weather benchmarks on Japanese society

    Mamoru Ishii, Daikou Shiota, Chihiro Tao, Yusuke Ebihara, Hitoshi Fujiwara, Takako Ishii, Kiyoshi Ichimoto, Ryuho Kataoka, Kiyokazu Koga, Yuki Kubo, Kanya Kusano, Yoshizumi Miyoshi, Tsutomu Nagatsuma, Aoi Nakamizo, Masao Nakamura, Michi Nishioka, Susumu Saito, Tatsuhiko Sato, Takuya Tsugawa, Shigeo Yoden

    EARTH PLANETS AND SPACE   Vol. 73 ( 1 )   2021.5

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    Language:Japanese   Publishing type:Research paper (scientific journal)   Publisher:SPRINGER  

    We surveyed the relationship between the scale of space weather events and their occurrence rate in Japan, and we discussed the social impact of these phenomena during the Project for Solar-Terrestrial Environment Prediction (PSTEP) in 2015-2019. The information was compiled for domestic users of space weather forecasts for appropriate preparedness against space weather disasters. This paper gives a comprehensive summary of the survey, focusing on the fields of electricity, satellite operations, communication and broadcasting, satellite positioning usage, aviation, human space activity, and daily life on the Earth's surface, using the cutting-edge knowledge of space weather. Quantitative estimations of the economic impact of space weather events on electricity supply and aviation are also given. Some topics requiring future research, which were identified during the survey are also described.

    DOI: 10.1186/s40623-021-01420-5

    Web of Science

  10. Solar Soft X-ray Irradiance Variability, I: Segmentation of Hinode/XRT Full-Disk Images and Comparison with GOES (1-8 angstrom) X-Ray Flux

    H. N. Adithya, Rangaiah Kariyappa, Imada Shinsuke, Kusano Kanya, Joe Zender, Luc Dame, Giono Gabriel, Edward DeLuca, Mark Weber

    SOLAR PHYSICS   Vol. 296 ( 4 )   2021.4

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    Language:English   Publishing type:Research paper (scientific journal)   Publisher:SPRINGER  

    It is of great interest and importance to study the variabilities of solar EUV, UV and X-ray irradiance in heliophysics, in Earth's climate, and space weather applications. A careful study is required to identify, track, monitor and segment the different coronal features such as active regions (ARs), coronal holes (CHs), the background regions (BGs) and the X-ray bright points (XBPs) from spatially resolved full-disk images of the Sun. Variability of solar soft X-ray irradiance is studied for a period of 13 years (February 2007-March 2020, covers Solar Cycle 24), using the X-Ray Telescope on board the Hinode (Hinode/XRT) and GOES (1 - 8 angstrom). The full-disk X-ray images observed in Al_mesh filter from XRT are used, for the first time, to understand the solar X-ray irradiance variability measured, Sun as a star, by GOES instrument. An algorithm in Python has been developed and applied to identify and segment coronal X-ray features (ARs, CHs, BGs, and XBPs) from the full-disk soft X-ray observations of Hinode/XRT. The segmentation process has been carried out automatically based on the intensity level, morphology and sizes of the X-ray features. The total intensity, area, and contribution of ARs/CHs/BGs/XBPs features were estimated and compared with the full-disk integrated intensity (FDI) and GOES (1 - 8 angstrom) X-ray irradiance measurements. The XBPs have been identified and counted automatically over the full disk to investigate their relation to solar magnetic cycle. The total intensity of ARs/CHs/BGs/XBPs/FD regions are compared with the GOES (1 - 8 angstrom) X-ray irradiance variations. We present the results obtained from Hinode/XRT full-disk images (in Al_mesh filter) and compare the resulting integrated full-disk intensity (FDI) with GOES X-ray irradiance. The X-ray intensity measured over ARs/CHs/BGs/XBPs/FD is well correlated with GOES X-ray flux. The contributions of the segmented X-ray features to FDI and X-ray irradiance variations are determined. It is found that the background and active regions have a greater impact on the X-ray irradiance fluctuations. The mean contribution estimated for the whole observed period of the background regions (BGs) will be around 65 +/- 10.97%, whereas the ARs, XBPs and CHs are 30 +/- 11.82%, 4 +/- 1.18% and 1 +/- 0.52%, respectively, to total solar X-ray flux. We observed that the area and contribution of ARs and CHs varies with the phase of the solar cycle, whereas the BGs and XBPs show an anti-correlation. We find that the area of the coronal features is highly variable suggesting that their area has to be taken into account in irradiance models, in addition to their intensity variations. The time series results of XBPs suggest for an existence of anti-correlation between the number of XBPs and the sunspot numbers. It is also important to consider both the number variation and the contribution of XBPs in the reconstruction of total solar X-ray irradiance variability.

    DOI: 10.1007/s11207-021-01785-6

    Web of Science

  11. Magnetic Helicity Flux across Solar Active Region Photospheres. II. Association of Hemispheric Sign Preference with Flaring Activity during Solar Cycle 24

    Sung-Hon Park, K. D. Leka, Kanya Kusano

    ASTROPHYSICAL JOURNAL   Vol. 911 ( 2 )   2021.4

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    Language:Japanese   Publishing type:Research paper (scientific journal)   Publisher:IOP PUBLISHING LTD  

    In our earlier study (Paper I) of this series, we examined the hemispheric sign preference (HSP) of magnetic helicity flux dH/dt across photospheric surfaces of 4802 samples of 1105 unique active regions (ARs) observed during solar cycle 24. Here, we investigate any association of the HSP, expressed as a degree of compliance, with flaring activity, analyzing the same set of dH/dt estimates as used in Paper I. The AR samples under investigation are assigned to heliographic regions (HRs) defined in the Carrington longitude-latitude plane with a grid spacing of 45 degrees in longitude and 15 degrees in latitude. For AR samples in each of the defined HRs, we calculate the degree of HSP compliance and the average soft X-ray flare index. The strongest flaring activity is found to be in one distinctive HR with an extremely low-HSP compliance of 41% as compared to the mean and standard deviation of 62% and 7%, respectively, over all HRs. This sole HR shows an anti-HSP (i.e., <50%) and includes the highly flare-productive AR NOAA 12673, however this AR is not uniquely responsible for the HR's low HSP. We also find that all HRs with the highest flaring activity are located in the southern hemisphere, and they tend to have lower degrees of HSP compliance. These findings point to the presence of localized regions of the convection zone with enhanced turbulence, imparting a greater magnetic complexity and a higher flaring rate to some rising magnetic flux tubes.

    DOI: 10.3847/1538-4357/abea13

    Web of Science

  12. Data-driven MHD Simulation of Successive Solar Plasma Eruptions

    Kaneko Takafumi, Park Sung-Hong, Kusano Kanya

    ASTROPHYSICAL JOURNAL   Vol. 909 ( 2 )   2021.3

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    Language:Japanese   Publishing type:Research paper (scientific journal)  

    DOI: 10.3847/1538-4357/abe414

    Web of Science

  13. Lagrangian chaotic saddles and objective vortices in solar plasmas

    Abraham C-L Chian, Suzana S. A. Silva, Erico L. Rempel, Luis R. Bellot Rubio, Milan Gosic, Kanya Kusano, Sung-Hong Park

    PHYSICAL REVIEW E   Vol. 102 ( 6 )   2020.12

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    Language:Japanese   Publishing type:Research paper (scientific journal)   Publisher:AMER PHYSICAL SOC  

    We report observational evidence of Lagrangian chaotic saddles in plasmas, given by the intersections of finite-time unstable and stable manifolds, using an approximate to 22h sequence of spacecraft images of the horizontal velocity field of solar photosphere. A set of 29 persistent objective vortices with lifetimes varying from 28.5 to 298.3 min are detected by computing the Lagrangian averaged vorticity deviation. The unstable manifold of the Lagrangian chaotic saddles computed for approximate to 11h exhibits twisted folding motions indicative of recurring vortices in a magnetic mixed-polarity region. We show that the persistent objective vortices are formed in the gap regions of Lagrangian chaotic saddles at supergranular junctions.

    DOI: 10.1103/PhysRevE.102.060201

    Web of Science

  14. Magnetic Helicity Flux across Solar Active Region Photospheres. I. Hemispheric Sign Preference in Solar Cycle 24

    Sung-Hong Park, K. D. Leka, Kanya Kusano

    ASTROPHYSICAL JOURNAL   Vol. 904 ( 1 )   2020.11

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    Language:Japanese   Publishing type:Research paper (scientific journal)   Publisher:IOP PUBLISHING LTD  

    A hemispheric preference in the dominant sign of magnetic helicity has been observed in numerous features in the solar atmosphere, i.e., left-handed/right-handed helicity in the northern/southern hemisphere. The relative importance of different physical processes that may contribute to the observed hemispheric sign preference (HSP) of magnetic helicity is still under debate. Here, we estimate magnetic helicity flux (dH/dt) across the photospheric surface for 4802 samples of 1105 unique active regions (ARs) that appeared over an 8 yr period from 2010 to 2017 during solar cycle 24, using photospheric vector magnetic field observations by the Helioseismic and Magnetic Imager (HMI) on board the Solar Dynamics Observatory (SDO). The estimates of dH/dt show that 63% and 65% of the investigated AR samples in the northern and southern hemispheres, respectively, follow the HSP. We also find a trend that the HSP of dH/dt increases from similar to 50%-60% up to similar to 70%-80% as ARs (1) appear at the earlier inclining phase of the solar cycle or higher latitudes and (2) have larger values of vertical bar dH/dt vertical bar, the total unsigned magnetic flux, and the average plasma-flow speed. These observational findings support the enhancement of the HSP mainly by the Coriolis force acting on a buoyantly rising and expanding flux tube through the turbulent convection zone. In addition, the differential rotation on the solar surface as well as the tachocline alpha-effect of a flux-transport dynamo may reinforce the HSP for ARs at higher latitudes.

    DOI: 10.3847/1538-4357/abbb93

    Web of Science

  15. Forward Modeling of Particle Acceleration and Transport in an Individual Solar Flare

    Mykola Gordovskyy, Philippa K. Browning, Satoshi Inoue, Eduard P. Kontar, Kanya Kusano, Grigory E. Vekstein

    ASTROPHYSICAL JOURNAL   Vol. 902 ( 2 )   2020.10

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    Language:Japanese   Publishing type:Research paper (scientific journal)   Publisher:IOP PUBLISHING LTD  

    The aim of this study is to generate maps of the hard X-ray emission produced by energetic electrons in a solar flare and compare them with observations. The ultimate goal is to test the viability of the combined MHD/test-particle approach for data-driven modeling of active events in the solar corona and their impact on the heliosphere. Based on an MHD model of X-class solar flare observed on 2017 September 8, we calculate trajectories of a large number of electrons and protons using the relativistic guiding-center approach. Using the obtained particle trajectories, we deduce the spatial and energy distributions of energetic electrons and protons, and calculate bremsstrahlung hard X-ray emission using the "thin-target" approximation. Our approach predicts some key characteristics of energetic particles in the considered flare, including the size and location of the acceleration region, energetic particle trajectories and energy spectra. Most importantly, the hard X-ray bremsstrahlung intensity maps predicted by the model are in good agreement with those observed by RHESSI. Furthermore, the locations of proton and electron precipitation appear to be close to the sources of helioseismic response detected in this flare. Therefore, the adopted approach can be used for observationally driven modeling of individual solar flares, including manifestations of energetic particles in the corona, as well as the inner heliosphere.

    DOI: 10.3847/1538-4357/abb60e

    Web of Science

  16. The Effects of Oscillations and Collisions of Emerging Bipolar Regions on the Triggering of Solar Flares

    Boocock C., Kusano K., Tsiklauri D.

    ASTROPHYSICAL JOURNAL   Vol. 900 ( 1 )   2020.9

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    Language:Japanese   Publishing type:Research paper (scientific journal)  

    DOI: 10.3847/1538-4357/aba61a

    Web of Science

  17. A New Parameter of the Photospheric Magnetic Field to Distinguish Eruptive-flare Producing Solar Active Regions Reviewed

    Pei Hsuan Lin, Kanya Kusano, Daikou Shiota, Satoshi Inoue, K. D. Leka, Yuta Mizuno

    Astrophysical Journal   Vol. 894 ( 1 )   2020.5

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    Language:Japanese   Publishing type:Research paper (scientific journal)  

    © 2020. The American Astronomical Society. All rights reserved. Solar flares and coronal mass ejections (CMEs) are eruptive phenomena caused by coronal magnetic fields. In particular, large eruptive events originate in active regions (AR) with strong surface magnetic fields. However, it is still unclear what determines the capability of an AR to specifically produce eruptive flares and CMEs, and this hinders our knowledge of the initiation mechanism for the eruptive component of these phenomena. In this study, we propose a new parameter r m to measure the possibility that a flare that occurs in an AR can be eruptive and produce a CME. The parameter r m is defined by the ratio of the magnetic flux of twist higher than a threshold T c to the surrounding-and specifically, the overlying-magnetic flux. The value of r m for each AR can be estimated using nonlinear force-free field extrapolation models of the coronal magnetic field. Based on the data obtained by the Solar Dynamics Observatory/Helioseismic and Magnetic Imager, we calculated the values of r m for 29 ARs at 51 times prior to flares larger than M5.0 class. We find that the footpoints of field lines with twist higher than 0.2 can represent the subsequent flare ribbons well, and field lines that overlie and "fence in" the highly twisted region will work to confine the eruption, generating confined flares. Discriminant function analysis is used to show that r m is moderately well able to distinguish ARs that have the capability of producing eruptive flares.

    DOI: 10.3847/1538-4357/ab822c

    Web of Science

    Scopus

  18. A Magnetohydrodynamic Relaxation Method for Non-force-free Magnetic Field in Magnetohydrostatic Equilibrium Reviewed

    Takahiro Miyoshi, Kanya Kusano, Satoshi Inoue

    ASTROPHYSICAL JOURNAL SUPPLEMENT SERIES   Vol. 247 ( 1 )   2020.3

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    Language:Japanese   Publishing type:Research paper (scientific journal)   Publisher:IOP PUBLISHING LTD  

    A nonlinear force-free field (NLFFF) extrapolation is widely used to reconstruct the three-dimensional magnetic field in the solar corona from the observed photospheric magnetic field. However, the pressure gradient and gravitational forces are ignored in the NLFFF model, even though the photospheric and chromospheric magnetic fields are not in general force-free. Here we develop a magnetohydrodynamic (MHD) relaxation method that reconstructs the solar atmospheric (chromospheric and coronal) magnetic field as a non-force-free magnetic field (NFFF) in magnetohydrostatic equilibrium where the Lorentz, pressure gradient, and gravitational forces are balanced. The system of basic equations for the MHD relaxation method is derived, and mathematical properties of the system are investigated. A robust numerical solver for the system is constructed based on the modern high-order shock capturing scheme. Two-dimensional numerical experiments that include the pressure gradient and gravitational forces are also demonstrated.

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  19. Serial Flaring in an Active Region: Exploring Why Only One Flare Is Eruptive Reviewed

    Magnus M. Woods, Satoshi Inoue, Louise K. Harra, Sarah A. Matthews, Kanya Kusano

    ASTROPHYSICAL JOURNAL   Vol. 890 ( 1 )   2020.2

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    Over a four hour period between 2014 June 12-13 a series of three flares were observed within AR 12087. This sequence of flares started with a non-eruptive M-class flare, followed by a non-eruptive C-class flare, and finally ended with a second C-class flare that had an associated filament eruption. In this paper we combine spectroscopic analysis of Interface Region Imaging Spectrometer observations of the Si IV line during the three flares along with a series of nonlinear force-free field (NLFFF) extrapolations in order to investigate the conditions that lead the final flare to be eruptive. From this analysis it is found to be unlikely that the eruption was triggered by either kink instability or by tether-cutting reconnection, allowing the flux rope to rise into a region where it would be susceptible to the torus instability. The NLFFF modeling does, however, suggest that the overlying magnetic field has a fan-spine topology, raising the possibility that breakout reconnection occurring during the first two flares weakened the overlying field, allowing the flux rope to erupt in the subsequent third flare.

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  20. A Comparison of Flare Forecasting Methods. IV. Evaluating Consecutive-day Forecasting Patterns Reviewed

    Sung-Hong Park, K. D. Leka, Kanya Kusano, Jesse Andries, Graham Barnes, Suzy Bingham, D. Shaun Bloomfield, Aoife E. McCloskey, Veronique Delouille, David Falconer, Peter T. Gallagher, Manolis K. Georgoulis, Yuki Kubo, Kangjin Lee, Sangwoo Lee, Vasily Lobzin, JunChul Mun, Sophie A. Murray, Tarek A. M. Hamad Nageem, Rami Qahwaji, Michael Sharpe, R. A. Steenburgh, Graham Steward, Michael Terkildsen

    ASTROPHYSICAL JOURNAL   Vol. 890 ( 2 )   2020.2

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    A crucial challenge to successful flare prediction is forecasting periods that transition between "flare-quiet" and "flare-active." Building on earlier studies in this series in which we describe the methodology, details, and results of flare forecasting comparison efforts, we focus here on patterns of forecast outcomes (success and failure) over multiday periods. A novel analysis is developed to evaluate forecasting success in the context of catching the first event of flare-active periods and, conversely, correctly predicting declining flare activity. We demonstrate these evaluation methods graphically and quantitatively as they provide both quick comparative evaluations and options for detailed analysis. For the testing interval 2016-2017, we determine the relative frequency distribution of two-day dichotomous forecast outcomes for three different event histories (i.e., event/event, no-event/event, and event/no-event) and use it to highlight performance differences between forecasting methods. A trend is identified across all forecasting methods that a high/low forecast probability on day 1 remains high/low on day 2, even though flaring activity is transitioning. For M-class and larger flares, we find that explicitly including persistence or prior flare history in computing forecasts helps to improve overall forecast performance. It is also found that using magnetic/modern data leads to improvement in catching the first-event/first-no-event transitions. Finally, 15% of major (i.e., M-class or above) flare days over the testing interval were effectively missed due to a lack of observations from instruments away from the Earth-Sun line.

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  21. What Can Be Learned from Modern Data?

    Kusano K., Cliver E., Hayakawa H., Kovaltsov G. A., Usoskin I. G.

    EXTREME SOLAR PARTICLE STORMS: THE HOSTILE SUN     2020

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    DOI: 10.1088/2514-3433/ab404ach2

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  22. 太陽活動による地球環境変動の解明

    草野完也, 堀田英之

    日本シミュレーション学会誌「シミュレーション」   Vol. 39 ( 2 ) page: .   2020

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  23. Onset Mechanism of M6.5 Solar Flare Observed in Active Region 12371 Reviewed

    Jihye Kang, Satoshi Inoue, Kanya Kusano, Sung Hong Park, Yong Jae Moon

    Astrophysical Journal   Vol. 887 ( 2 )   2019.12

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    © 2019. The American Astronomical Society. All rights reserved. We studied a flare onset process in terms of stability of a three-dimensional (3D) magnetic field in active region 12371 producing an eruptive M6.5 flare in 2015 June 22. In order to reveal the 3D magnetic structure, we first extrapolated the 3D coronal magnetic fields based on time series of the photospheric vector magnetic fields under a nonlinear force-free field (NLFFF) approximation. The NLFFFs nicely reproduced the observed sigmoidal structure which is widely considered to be preeruptive magnetic configuration. In particular, we found that the sigmoid is composed of two branches of sheared arcade loops. On the basis of the NLFFFs, we investigated the sheared arcade loops to explore the onset process of the eruptive flare using three representative magnetohydrodynamic instabilities: the kink, torus, and double arc instabilities (DAI). The DAI, recently proposed by Ishiguro & Kusano, is a double arc loop that can be more easily destabilized than a torus loop. Consequently, the NLFFFs are found to be quite stable against the kink and torus instabilities. However, the sheared arcade loops formed prior to the flare possibly become unstable against the DAI. As a possible scenario for the onset process of the M6.5 flare, we suggest a three-step process: (1) double arc loops are formed by the sheared arcade loops through the tether-cutting reconnection during an early phase of the flare, (2) the DAI contributes to the expansion of destabilized double arc loops, and (3) finally, the torus instability makes the full eruption.

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  24. Supergranular turbulence in the quiet Sun: Lagrangian coherent structures (vol 488, pg 3076, 2019) Reviewed

    Chian Abraham C. -L, Silva Suzana S. A, Rempel Erico L, Gosic Milan, Bellot Rubio Luis R, Kusano Kanya, Miranda Rodrigo A, Requerey Iker S

    MONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY   Vol. 489 ( 1 ) page: 707 - 707   2019.10

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    © 2019 The Author(s) Published by Oxford University Press on behalf of the Royal Astronomical Society This is an erratum to the paper 'Supergranular turbulence in the quiet Sun: Lagrangian coherent structures' that was published in MNRAS, 488, 3076-3088 (2019). In the original version of stz1909, there were several instances where the author's corrections had not been implemented during the proofing stages. These have now been corrected as follows: (i) Page 3077: in the second paragraph, the reference 'G16 G17' has been corrected to 'Gošić et al. 2014, 2016'. (ii) Page 3079: in section 3.1, the reference 'G20' has been corrected to 'Haller (2015)'. (iii) Page 3087: the article ID 'eeau2307' has been added to reference 'Hotta H., Iijima H., Kusano K., 2019, Sci. Adv., 5'. The publisher apologises for these errors.

    DOI: 10.1093/mnras/stz2296

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  25. Supergranular turbulence in the quiet Sun: Lagrangian coherent structures Reviewed

    Abraham C.L. Chian, Suzana S.A. Silva, Erico L. Rempel, Milan Gošić, Luis R. Bellot Rubio, Kanya Kusano, Rodrigo A. Miranda, Iker S. Requerey

    Monthly Notices of the Royal Astronomical Society   Vol. 488 ( 3 ) page: 3076 - 3088   2019.9

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    © 2019 The Author(s) Published by Oxford University Press on behalf of the Royal Astronomical Society The quiet Sun exhibits a wealth of magnetic activities that are fundamental for our understanding of solar magnetism. The magnetic fields in the quiet Sun are observed to evolve coherently, interacting with each other to form prominent structures as they are advected by photospheric flows. The aim of this paper is to study supergranular turbulence by detecting Lagrangian coherent structures (LCS) based on the horizontal velocity fields derived from Hinode intensity images at disc centre of the quiet Sun on 2010 November 2. LCS act as transport barriers and are responsible for attracting/repelling the fluid elements and swirling motions in a finite time. Repelling/attracting LCS are found by computing the forward/backward finite-time Lyapunov exponent (FTLE), and vortices are found by the Lagrangian-averaged vorticity deviation method. We show that the Lagrangian centres and boundaries of supergranular cells are given by the local maximum of the forward and backward FTLE, respectively. The attracting LCS expose the location of the sinks of photospheric flows at supergranular junctions, whereas the repelling LCS interconnect the Lagrangian centres of neighbouring supergranular cells. Lagrangian transport barriers are found within a supergranular cell and from one cell to other cells, which play a key role in the dynamics of internetwork and network magnetic elements. Such barriers favour the formation of vortices in supergranular junctions. In particular, we show that the magnetic field distribution in the quiet Sun is determined by the combined action of attracting/repelling LCS and vortices.

    DOI: 10.1093/mnras/stz1909

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  26. A Comparison of Flare Forecasting Methods. III. Systematic Behaviors of Operational Solar Flare Forecasting Systems Reviewed

    K. D. Leka, Sung Hong Park, Kanya Kusano, Jesse Andries, Graham Barnes, Suzy Bingham, D. Shaun Bloomfield, Aoife E. McCloskey, Veronique Delouille, David Falconer, Peter T. Gallagher, Manolis K. Georgoulis, Yuki Kubo, Kangjin Lee, Sangwoo Lee, Vasily Lobzin, Junchul Mun, Sophie A. Murray, Tarek A.M. Hamad Nageem, Rami Qahwaji, Michael Sharpe, Robert A. Steenburgh, Graham Steward, Michael Terkildsen

    Astrophysical Journal   Vol. 881 ( 2 )   2019.8

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    © 2019. The American Astronomical Society. All rights reserved. A workshop was recently held at Nagoya University (2017 October 31-November 2), sponsored by the Center for International Collaborative Research, at the Institute for Space-Earth Environmental Research, Nagoya University, Japan, to quantitatively compare the performance of today's operational solar flare forecasting facilities. Building upon Paper I of this series, in Paper II we described the participating methods for this latest comparison effort, the evaluation methodology, and presented quantitative comparisons. In this paper, we focus on the behavior and performance of the methods when evaluated in the context of broad implementation differences. Acknowledging the short testing interval available and the small number of methods available, we do find that forecast performance: (1) appears to improve by including persistence or prior flare activity, region evolution, and a human "forecaster in the loop"; (2) is hurt by restricting data to disk-center observations; (3) may benefit from long-term statistics but mostly when then combined with modern data sources and statistical approaches. These trends are arguably weak and must be viewed with numerous caveats, as discussed both here and in Paper II. Following this present work, in Paper IV (Park et al. 2019) we will present a novel analysis method to evaluate temporal patterns of forecasting errors of both types (i.e., misses and false alarms). Hence, most importantly, with this series of papers, we demonstrate the techniques for facilitating comparisons in the interest of establishing performance-positive methodologies.

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  27. A Comparison of Flare Forecasting Methods. II. Benchmarks, Metrics, and Performance Results for Operational Solar Flare Forecasting Systems Reviewed

    K. D. Leka, Sung Hong Park, Kanya Kusano, Jesse Andries, Graham Barnes, Suzy Bingham, D. Shaun Bloomfield, Aoife E. McCloskey, Veronique Delouille, David Falconer, Peter T. Gallagher, Manolis K. Georgoulis, Yuki Kubo, Kangjin Lee, Sangwoo Lee, Vasily Lobzin, Junchul Mun, Sophie A. Murray, Tarek A.M. Hamad Nageem, Rami Qahwaji, Michael Sharpe, Robert A. Steenburgh, Graham Steward, Michael Terkildsen

    Astrophysical Journal, Supplement Series   Vol. 243 ( 2 )   2019.8

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    © 2019. The American Astronomical Society. All rights reserved.. Solar flares are extremely energetic phenomena in our solar system. Their impulsive and often drastic radiative increases, particularly at short wavelengths, bring immediate impacts that motivate solar physics and space weather research to understand solar flares to the point of being able to forecast them. As data and algorithms improve dramatically, questions must be asked concerning how well the forecasting performs; crucially, we must ask how to rigorously measure performance in order to critically gauge any improvements. Building upon earlier-developed methodology of Paper I (Barnes et al. 2016), international representatives of regional warning centers and research facilities assembled in 2017 at the Institute for Space-Earth Environmental Research, Nagoya University, Japan to, for the first time, directly compare the performance of operational solar flare forecasting methods. Multiple quantitative evaluation metrics are employed, with the focus and discussion on evaluation methodologies given the restrictions of operational forecasting. Numerous methods performed consistently above the "no-skill" level, although which method scored top marks is decisively a function of flare event definition and the metric used; there was no single winner. Following in this paper series, we ask why the performances differ by examining implementation details (Leka et al. 2019), and then we present a novel analysis method to evaluate temporal patterns of forecasting errors in Paper IV (Park et al. 2019). With these works, this team presents a well-defined and robust methodology for evaluating solar flare forecasting methods in both research and operational frameworks and today's performance benchmarks against which improvements and new methods may be compared.

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  28. Mechanism of non-steady Petschek-type reconnection with uniform resistivity Reviewed

    Takuya Shibayama, Kanya Kusano, Takahiro Miyoshi, Amitava Bhattacharjee

    PHYSICS OF PLASMAS   Vol. 26 ( 3 )   2019.3

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    The Sweet-Parker and Petschek models are well-established magnetohydrodynamics (MHD) models of steady magnetic reconnection. Recent findings on magnetic reconnection in high-Lundquist-number plasmas indicate that Sweet-Parker-type reconnection in marginally stable thin current sheets connecting plasmoids can produce fast reconnection. By contrast, it has proven difficult to achieve Petschek-type reconnection in plasmas with uniform resistivity because sustaining it requires localization of the diffusion region. However, Shibayama et al. [Phys. Plasmas 22, 100706 (2015)] recently noted that Petschek-type reconnection can he achieved spontaneously in a dynamical manner even under uniform resistivity through what they called dynamical Petschek reconnection. In this new type of reconnection, Petschek-type diffusion regions can be formed in connection with plasmoids. In this paper, we report the results of two-dimensional resistive MHD simulation with uniform resistivity, undertaken to determine the diffusion region localization mechanism under dynamical Petschek reconnection. Through this modeling, we found that the separation of the X-point from the flow stagnation point (S-point) plays a crucial role in the localization of the diffusion region because the motion of the X-point is restricted by the strong flow emanating from the flow stagnation point. This mechanism suggests that dynamical Petschek reconnection is possible even in large systems such as the solar corona. Published under license by AIP Publishing.

    DOI: 10.1063/1.5084771

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  29. Semiconservative reduced speed of sound technique for low Mach number flows with large density variations Reviewed

    Iijima, H, Hotta, H, Imada, S, Kusano, K, Shiota, D

    Astronomy & Astrophysics   Vol. 662   page: A157 - A157   2019.2

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    <italic>Context.</italic> The reduced speed of sound technique (RSST) has been used for efficient simulation of low Mach number flows in solar and stellar convection zones. The basic RSST equations are hyperbolic and are suitable for parallel computation by domain decomposition. The application of RSST is limited to cases in which density perturbations are much smaller than the background density. In addition, nonconservative variables are required to be evolved using this method, which is not suitable in cases where discontinuities such as shock waves coexist in a single numerical domain.


    <italic>Aims.</italic> In this study, we suggest a new semiconservative formulation of the RSST that can be applied to low Mach number flows with large density variations.


    <italic>Methods.</italic> We derive the wave speed of the original and newly suggested methods to clarify that these methods can reduce the speed of sound without affecting the entropy wave. The equations are implemented using the finite volume method. Several numerical tests are carried out to verify the suggested methods.


    <italic>Results.</italic> The analysis and numerical results show that the original RSST is not applicable when mass density variations are large. In contrast, the newly suggested methods are found to be efficient in such cases. We also suggest variants of the RSST that conserve momentum in the machine precision. The newly suggested variants are formulated as semiconservative equations, which reduce to the conservative form of the Euler equations when the speed of sound is not reduced. This property is advantageous when both high and low Mach number regions are included in the numerical domain.


    <italic>Conclusions.</italic> The newly suggested forms of RSST can be applied to a wider range of low Mach number flows.

    DOI: 10.1051/0004-6361/201834031

  30. Weak influence of near-surface layer on solar deep convection zone revealed by comprehensive simulation from base to surface Reviewed

    H. Hotta, H. Iijima, K. Kusano

    Science Advances   Vol. 5 ( 1 )   2019.1

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    Copyright © 2019 The Authors. The solar convection zone is filled with turbulent convection in highly stratified plasma. Several theoretical and observational studies suggest that the numerical calculations overestimate the convection velocity. Since all deep convection zone calculations exclude the solar surface due to substantial temporal and spatial scale separations, the solar surface, which drives the thermal convection with efficient radiative cooling, has been thought to be the key to solve this discrepancy. Thanks to the recent development in massive supercomputers, we are successful in performing the comprehensive calculation covering the whole solar convection zone. We compare the results with and without the solar surface in the local domain and without the surface in the full sphere. The calculations do not include the rotation and the magnetic field. The surface region has an unexpectedly weak influence on the deep convection zone. We find that just including the solar surface cannot solve the problem.

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  31. Onset mechanism of solar eruptions Reviewed

    Satoshi Inoue, Yumi Bamba, Kanya Kusano

    Journal of Atmospheric and Solar-Terrestrial Physics   Vol. 180   page: 3 - 8   2018.11

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    © 2017 Elsevier Ltd Solar eruptions are the most energetic phenomena observed in the solar system observed as flares, coronal mass ejections (CMEs) and filament/prominence eruption. The helically twisted flux tube is widely thought to be the source and driver of solar eruptions and to carry the plasma into the interplanetary space. Those may eventually reach the magnetosphere and cause strong disturbances of the geomagnetic field. Therefore, the understanding of the onset of solar eruptions is important not only in the framework of solar physics but also for the space weather forecast. In this paper, we report on new insight into the onset mechanism of solar eruptions recently obtained from our new studies. We perform the studies in terms of the observational approach with state-of-the-art solar physics satellites and the numerical one with the latest super computer system. We specified two types of small magnetic perturbations of the photospheric magnetic field. These can enhance the magnetic reconnection in the pre-existing non-potential magnetic field, which produces a large flux tube and then drives the eruption. We further confirmed that this reconnection is a key process for the eruption in our latest data-constrained simulation. We report our latest results and our interpretation of the onset mechanism of solar eruptions.

    DOI: 10.1016/j.jastp.2017.08.035

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  32. A Study of Magnetic Field Characteristics of the Flaring Active Region Based on Nonlinear Force-free Field Extrapolation Reviewed

    Johan Muhamad, Kanya Kusano, Satoshi Inoue, Yumi Bamba

    ASTROPHYSICAL JOURNAL   Vol. 863 ( 2 )   2018.8

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    Coronal magnetic fields are responsible for the onset of solar flares and solar eruptions. However, the type of magnetic field parameters that can be used to measure the critical condition for a solar eruption is still unclear. As an effort to understand the possible condition for a solar flare, we have examined the nondimensional parameter kappa introduced by Ishiguro & Kusano, which contains information about magnetic twist distribution and magnetic flux in an active region (AR). We introduce a new parameter kappa*, as a proxy for kappa, and we have analyzed the evolution of kappa* during the flaring period of an AR using the nonlinear force-free field extrapolated from the photospheric vector magnetic field data. Using data from the Solar Dynamics Observatory/Helioseismic and Magnetic Imager, we have calculated kappa* for the AR NOAA 11158 during its three-day flaring period. We found that kappa* increased to a certain level before two large flares and decreased significantly after their onset. The results suggest that kappa* may be used as an indicator of the necessary condition for the onset of a solar eruption in the AR. Based on this result, we propose a new method to assess the possibility of a large solar eruption from an AR by combining the parameter kappa* and information about the magnetic energy of the AR.

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  33. The Triggering of the 2014 March 29 Filament Eruption Reviewed

    Magnus M. Woods, Satoshi Inoue, Louise K. Harra, Sarah A. Matthews, Kanya Kusano, Nadine M. E. Kalmoni

    ASTROPHYSICAL JOURNAL   Vol. 860 ( 2 )   2018.6

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    The X1 flare and associated filament eruption occurring in NOAA Active Region 12017 on SOL2014-03-29 has been a source of intense study. In this work, we analyze the results of a series of nonlinear force-free field extrapolations of the flare's pre- and post-flare periods. In combination with observational data provided by the IRIS, Hinode, and Solar Dynamics Observatory missions, we have confirmed the existence of two flux ropes present within the active region prior to flaring. Of these two flux ropes, we find that intriguingly only one erupts during the X1 flare. We propose that the reason for this is due to tether cutting reconnection allowing one of the flux ropes to rise to a torus unstable region prior to flaring, thus allowing it to erupt during the subsequent flare.

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  34. Coronal mass ejection hits mercury: A.I.K.E.F. hybrid-code results compared to MESSENGER data Reviewed

    W. Exner, D. Heyner, L. Liuzzo, U. Motschmann, D. Shiota, K. Kusano, T. Shibayama

    Planetary and Space Science   Vol. 153   page: 89 - 99   2018.4

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    © 2018 Elsevier Ltd Mercury is the closest orbiting planet around the sun and is therefore embedded in an intensive and highly varying solar wind. In-situ data from the MESSENGER spacecraft of the plasma environment near Mercury indicates that a coronal mass ejection (CME) passed the planet on 23 November 2011 over the span of the 12 h MESSENGER orbit. Slavin et al. (2014) derived the upstream parameters of the solar wind at the time of that orbit, and were able to explain the observed MESSENGER data in the cusp and magnetopause segments of MESSENGER's trajectory. These upstream parameters will be used for our first simulation run. We use the hybrid code A.I.K.E.F. which treats ions as individual particles and electrons as a mass-less fluid, to conduct hybrid simulations of Mercury's magnetospheric response to the impact of the CME on ion gyro time scales. Results from the simulation are in agreement with magnetic field measurements from the inner day-side magnetosphere and the bow-shock region. However, at the planet's nightside, Mercury's plasma environment seemed to be governed by different solar wind conditions, in conclusion, Mercury's interaction with the CME is not sufficiently describable by only one set of upstream parameters. Therefore, to simulate the magnetospheric response while MESSENGER was located in the tail region, we use parameters obtained from the MHD solar wind simulation code SUSANOO (Shiota et al. (2014)) for our second simulation run. The parameters of the SUSANOO model achieve a good agreement of the data concerning the plasma tail crossing and the night-side approach to Mercury. However, the polar and closest approach are hardly described by both upstream parameters, namely, neither upstream dataset is able to reproduce the MESSENGER crossing of Mercury's magnetospheric cusp. We conclude that the respective CME was too variable on the timescale of the MESSENGER orbit to be described by only two sets of upstream conditions. Our results suggest locally strong and highly variable dynamics of the CME on timescales of 15 min while MESSENGER was near closest approach.

    DOI: 10.1016/j.pss.2017.12.016

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  35. Evaluation of Applicability of a Flare Trigger Model Based on a Comparison of Geometric Structures Reviewed

    Yumi Bamba, Kanya Kusano

    Astrophysical Journal   Vol. 856 ( 1 )   2018.3

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    © 2018. The American Astronomical Society. All rights reserved. The triggering mechanism(s) and critical condition(s) of solar flares are still not completely clarified, although various studies have attempted to elucidate them. We have also proposed a theoretical flare-trigger model based on MHD simulations in which two types of small-scale bipole fields, the so-called opposite polarity (OP) and reversed shear (RS), can trigger flares. In this study, we evaluated the applicability of our flare-trigger model to the observation of 32 flares that were observed by the Solar Dynamics Observatory, by focusing on geometrical structures. We classified the events into six types, including the OP and RS types, based on photospheric magnetic field configuration, presence of precursor brightenings, and shape of the initial flare ribbons. As a result, we found that approximately 30% of the flares were consistent with our flare-trigger model, and the number of RS-type triggered flares is larger than that of the OP type. We found that none of the sampled events contradict our flare model; though, we cannot clearly determine the trigger mechanism of 70% of the flares in this study. We carefully investigated the applicability of our flare-trigger model and the possibility that other models can explain the other 70% of the events. Consequently, we concluded that our flare-trigger model has certainly proposed important conditions for flare-triggering.

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  36. Formation and dynamics of a solar eruptive flux tube Reviewed

    Satoshi Inoue, Kanya Kusano, Jörg Büchner, Jan Skála

    Nature Communications   Vol. 9 ( 1 )   2018.1

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    © The Author(s) 2018. Solar eruptions are well-known drivers of extreme space weather, which can greatly disturb the Earth's magnetosphere and ionosphere. The triggering process and initial dynamics of these eruptions are still an area of intense study. Here we perform a magnetohydrodynamic simulation taking into account the observed photospheric magnetic field to reveal the dynamics of a solar eruption in a real magnetic environment. In our simulation, we confirmed that tether-cutting reconnection occurring locally above the polarity inversion line creates a twisted flux tube, which is lifted into a toroidal unstable area where it loses equilibrium, destroying the force-free state, and driving the eruption. Consequently, a more highly twisted flux tube is built up during this initial phase, which can be further accelerated even when it returns to a stable area. We suggest that a nonlinear positive feedback process between the flux tube evolution and reconnection is the key to ensure this extra acceleration.

    DOI: 10.1038/s41467-017-02616-8

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  37. Improvement of solar-cycle prediction: Plateau of solar axial dipole moment

    H. Iijima, H. Hotta, S. Imada, K. Kusano, D. Shiota

    Astronomy and Astrophysics   Vol. 607   2017.11

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    © ESO, 2017. Aims. We report the small temporal variation of the axial dipole moment near the solar minimum and its application to the solar-cycle prediction by the surface flux transport (SFT) model. Methods. We measure the axial dipole moment using the photospheric synoptic magnetogram observed by the Wilcox Solar Observatory (WSO), the ESA/NASA Solar and Heliospheric Observatory Michelson Doppler Imager (MDI), and the NASA Solar Dynamics Observatory Helioseismic and Magnetic Imager (HMI). We also use the SFT model for the interpretation and prediction of the observed axial dipole moment. Results. We find that the observed axial dipole moment becomes approximately constant during the period of several years before each cycle minimum, which we call the axial dipole moment plateau. The cross-equatorial magnetic flux transport is found to be small during the period, although a significant number of sunspots are still emerging. The results indicate that the newly emerged magnetic flux does not contribute to the build up of the axial dipole moment near the end of each cycle. This is confirmed by showing that the time variation of the observed axial dipole moment agrees well with that predicted by the SFT model without introducing new emergence of magnetic flux. These results allow us to predict the axial dipole moment at the Cycle 24/25 minimum using the SFT model without introducing new flux emergence. The predicted axial dipole moment at the Cycle 24/25 minimum is 60-80 percent of Cycle 23/24 minimum, which suggests the amplitude of Cycle 25 is even weaker than the current Cycle 24. Conclusions. The plateau of the solar axial dipole moment is an important feature for the longer-term prediction of the solar cycle based on the SFT model.

    DOI: 10.1051/0004-6361/201731813

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  38. Taylor problem and onset of plasmoid instability in the Hall-magnetohydrodynamics Reviewed

    G. Vekstein, K. Kusano

    Physics of Plasmas   Vol. 24 ( 10 )   2017.10

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    © 2017 Author(s). A well-known Taylor problem in the theory of forced magnetic reconnection is investigated in the framework of the Hall-Magnetohydrodynamics. In the first part of the paper, we deal with the linear theory of the Hall-mediated forced reconnection. Then, in the second part, these results are used for demonstrating how the secondary tearing (plasmoid) instability can develop in the course of this process.

    DOI: 10.1063/1.4996982

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    Scopus

  39. Double Arc Instability in the Solar Corona Reviewed

    N. Ishiguro, K. Kusano

    ASTROPHYSICAL JOURNAL   Vol. 843 ( 2 )   2017.7

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    The stability of the magnetic field in the solar corona is important for understanding the causes of solar eruptions. Although various scenarios have been suggested to date, the tether-cutting reconnection scenario proposed by Moore et al. is one of the widely accepted models to explain the onset process of solar eruptions. Although the tether-cutting reconnection scenario proposes that the sigmoidal field formed by internal reconnection is the magnetic field in the pre-eruptive state, the stability of the sigmoidal field has not yet been investigated quantitatively. In this paper, in order to elucidate the stability problem of. the pre-eruptive state, we developed a simple numerical analysis in which the sigmoidal field is modeled by a double arc electric current loop and its stability is analyzed. As a result, we found that the double arc loop is more easily destabilized than the axisymmetric torus, and it becomes unstable even if the external field does not decay with altitude, which is in contrast to the axisymmetric torus instability. This suggests that tether-cutting reconnection may well work as the onset mechanism of solar eruptions, and if so, the critical condition for eruption under a certain geometry may be determined by a new type of instability rather than by the torus instability. Based on them, we propose a new type of instability called double arc instability (DAI). We discuss the critical conditions for DAI and derive a new parameter k, defined as the product of the magnetic twist and the normalized flux of the tether-cutting reconnection.

    DOI: 10.3847/1538-4357/aa799b

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  40. Magnetohydrodynamic Simulations for Studying Solar Flare Trigger Mechanism Reviewed

    J. Muhamad, K. Kusano, S. Inoue, D. Shiota

    ASTROPHYSICAL JOURNAL   Vol. 842 ( 2 )   2017.6

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    In order to understand the flare trigger mechanism, we conduct three-dimensional magnetohydrodynamic simulations using a coronal magnetic field model derived from data observed by the Hinode satellite. Several types of magnetic bipoles are imposed into the photospheric boundary of the Nonlinear Force-free Field model of Active Region (AR) NOAA 10930 on 2006 December 13, to investigate what kind of magnetic disturbance may trigger the flare. As a result, we confirm that certain small bipole fields, which emerge into the highly sheared global magnetic field of an AR, can effectively trigger a flare. These bipole fields can be classified into two groups based on their orientation relative to the polarity inversion line: the so-called opposite polarity, and reversed shear structures, as suggested by Kusano et al. We also investigate the structure of the footpoints of reconnected field lines. By comparing the distribution of reconstructed field lines and observed flare ribbons, the trigger structure of the flare can be inferred. Our simulation suggests that the data-constrained simulation, taking into account both the large-scale magnetic structure and small-scale magnetic disturbance (such as emerging fluxes), is a good way to discover a flare-producing AR, which can be applied to space weather prediction.

    DOI: 10.3847/1538-4357/aa750e

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  41. Study on Precursor Activity of the X1.6 Flare. in the Great AR 12192 with SDO, IRIS, and Hinode Reviewed

    Yumi Bamba, Kyoung-Sun Lee, Shinsuke Imada, Kanya Kusano

    ASTROPHYSICAL JOURNAL   Vol. 840 ( 2 )   2017.5

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    The physical properties and their. contribution to the onset of a solar flare are still uncleare even. though chromospheric brightening is considered a precursor phenomenon of a flare. Many studies suggested that photospheric magnetic field changes cause destabilization of large-scale coronal structure. We aim to understand how a small photospheric change contributes to a flare and to reveal how the intermediary chromosphere behaves in the precursor phase. We analyzed the precursor brightening of the X1.6 flare on 2014 October 22 in the AR 12192 using the Interface Region Imaging Spectrograph (IRIS) and Hinode/EUV Imaging Spectrometer (EIS) data. We investigated a localized jet with the strong precursor brightening, and compared the intensity, Doppler velocity, and line width in C II, Mg II k, and. Si IV lines by IRIS and He II, Fe XII, and. Fe XV lines by Hinode/EIS. We also analyzed the photospheric magnetic field and chromospheric/coronal structures using the. Solar Dynamics Observatory (SDO)/Helioseismic and Magnetic Imager and Atmospheric Imaging Assembly. We found a significant blueshift (similar to 100 km s(-1)), which is related to the strong precursor brightening over a characteristic magnetic field structure, and the blueshift was observed at all of. the temperatures. This might indicate that the flow is accelerated by Lorentz force. Moreover, the large-scale coronal loop that connects the foot points of the flare ribbons was destabilized just after the precursor brightening with the blueshift. It suggests that magnetic reconnection locally occurred in the lower chromosphere and it triggered magnetic reconnection of the X1.6 flare in the corona.

    DOI: 10.3847/1538-4357/aa6dfe

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  42. High-resolution observations of flare precursors in the low solar atmosphere

    Wang Haimin, Liu Chang, Ahn Kwangsu, Xu Yan, Jing Ju, Deng Na, Huang Nengyi, Liu Rui, Kusano Kanya, Fleishman Gregory D., Gary Dale E., Cao Wenda

    NATURE ASTRONOMY   Vol. 1 ( 5 )   2017.5

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    DOI: 10.1038/s41550-017-0085

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  43. Triggering Process of the X1.0 Three-ribbon Flare in the Great Active Region NOAA 12192 Reviewed

    Yumi Bamba, Satoshi Inoue, Kanya Kusano, Daikou Shiota

    ASTROPHYSICAL JOURNAL   Vol. 838 ( 2 )   2017.4

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    The solar magnetic field in a flare-producing active region (AR) is much more complicated than theoretical models, which assume a very simple magnetic field structure. The X1.0 flare, which occurred in AR 12192 on 2014 October 25, showed a complicated three-ribbon structure. To clarify the trigger process of the flare and to evaluate the applicability of a simple theoretical model, we analyzed the data from Hinode/Solar Optical Telescope and the Solar Dynamics Observatory/Helioseismic and Magnetic Imager, Atmospheric Imaging Assembly. We investigated the spatio-temporal correlation between the magnetic field structures, especially the non-potentiality of the horizontal field, and the bright structures in the solar atmosphere. As a result, we determined that the western side of the positive polarity, which is intruding on a negative polarity region, is the location where the flare was triggered. This is due to the fact that the sign of the. magnetic shear in that region was opposite that of. the major shear of the AR, and the significant brightenings were observed over the polarity inversion line (PIL) in that region before flare onset. These features are consistent with the recently proposed flare-trigger model that suggests that small reversed shear (RS) magnetic disturbances can trigger solar flares. Moreover, we found that the RS field was located slightly off the flaring PIL, contrary to the theoretical prediction. We discuss the possibility of an extension of the RS model based on an extra numerical simulation. Our result suggests that the RS field has a certain flexibility for displacement from a highly sheared PIL, and that the RS field triggers more flares than we expected.

    DOI: 10.3847/1538-4357/aa6682

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  44. High-resolution observations of flare precursors in the low solar atmosphere Reviewed

    Haimin Wang, Chang Liu, Kwangsu Ahn, Yan Xu, Ju Jing, Na Deng, Nengyi Huang, Rui Liu, Kanya Kusano, Gregory D. Fleishman, Dale E. Gary & Wenda Cao

    Nature Astronomy   Vol. 1   page: 0085   2017.3

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    DOI: 10.1038/s41550-017-0085

  45. SIMULATION STUDY OF HEMISPHERIC PHASE-ASYMMETRY IN THE SOLAR CYCLE Reviewed

    D. Shukuya, K. Kusano

    ASTROPHYSICAL JOURNAL   Vol. 835 ( 1 )   2017.1

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    Observations of the Sun suggest that solar activities systematically create north-south hemispheric asymmetries. For instance, the hemisphere in which sunspot activity is more active tends to switch after the early half of each solar cycle. Svalgaard & Kamide recently pointed out that the time gaps of polar field reversal between the northern and southern hemispheres are simply consequences of the asymmetry of sunspot activity. However, the mechanism underlying the asymmetric feature in solar cycle activity is not yet well understood. In this paper, in order to explain the cause of the asymmetry from the theoretical point of view, we investigate the relationship between the dipole- and quadrupole-type components of the magnetic field in the solar cycle using the mean-field theory based on the flux transport dynamo model. As a result, we found that there are two different attractors of the solar cycle, in which either the north or the south polar field is first reversed, and that the flux transport dynamo model explains well the phase-asymmetry of sunspot activity and the polar field reversal without any ad hoc source of asymmetry.

    DOI: 10.3847/1538-4357/835/1/84

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  46. Toward the Understanding and Prediction of Solar-terrestrial Environment Variabilities

    KUSANO Kanya

    Aeronautical and Space Sciences Japan   Vol. 65 ( 1 ) page: 22 - 25   2017

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    Language:Japanese   Publishing type:Research paper (scientific journal)   Publisher:THE JAPAN SOCIETY FOR AERONAUTICAL AND SPACE SCIENCES  

    DOI: 10.14822/kjsass.65.1_22

    CiNii Books

  47. The Characteristics of Solar X-Class Flares and CMEs: A Paradigm for Stellar Superflares and Eruptions? Reviewed

    Louise K. Harra, Carolus J. Schrijver, Miho Janvier, Shin Toriumi, Hugh Hudson, Sarah Matthews, Magnus M. Woods, Hirohisa Hara, Manuel Guedel, Adam Kowalski, Rachel Osten, Kanya Kusano, Theresa Lueftinger

    SOLAR PHYSICS   Vol. 291 ( 6 ) page: 1761 - 1782   2016.8

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    This paper explores the characteristics of 42 solar X-class flares that were observed between February 2011 and November 2014, with data from the Solar Dynamics Observatory (SDO) and other sources. This flare list includes nine X-class flares that had no associated CMEs. In particular our aim was to determine whether a clear signature could be identified to differentiate powerful flares that have coronal mass ejections (CMEs) from those that do not. Part of the motivation for this study is the characterization of the solar paradigm for flare/CME occurrence as a possible guide to the stellar observations; hence we emphasize spectroscopic signatures. To do this we ask the following questions: Do all eruptive flares have long durations? Do CME-related flares stand out in terms of active-region size vs. flare duration? Do flare magnitudes correlate with sunspot areas, and, if so, are eruptive events distinguished? Is the occurrence of CMEs related to the fraction of the active-region area involved? Do X-class flares with no eruptions have weaker non-thermal signatures? Is the temperature dependence of evaporation different in eruptive and non-eruptive flares? Is EUV dimming only seen in eruptive flares? We find only one feature consistently associated with CME-related flares specifically: coronal dimming in lines characteristic of the quiet-Sun corona, i.e. 1 - 2 MK. We do not find a correlation between flare magnitude and sunspot areas. Although challenging, it will be of importance to model dimming for stellar cases and make suitable future plans for observations in the appropriate wavelength range in order to identify stellar CMEs consistently.

    DOI: 10.1007/s11207-016-0923-0

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  48. STRUCTURE AND STABILITY OF MAGNETIC FIELDS IN SOLAR ACTIVE REGION 12192 BASED ON NONLINEAR FORCE-FREE FIELD MODELING Reviewed

    S. Inoue, K. Hayashi, K. Kusano

    ASTROPHYSICAL JOURNAL   Vol. 818 ( 2 ) page: ir. 168, 11   2016.2

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    We analyze a three-dimensional (3D) magnetic structure and its stability in large solar active region (AR) 12192, using the 3D coronal magnetic field constructed under a nonlinear force-free field (NLFFF) approximation. In particular, we focus on the magnetic structure that produced an X3.1-class flare, which is one of the X-class flares observed in AR 12192. According to our analysis, the AR contains a multiple-flux-tube system, e.g., a large flux tube, with footpoints that are anchored to the large bipole field, under which other tubes exist close to a polarity inversion line (PIL). These various flux tubes of different sizes and shapes coexist there. In particular, the latter are embedded along the PIL, which produces a favorable shape for the tether-cutting reconnection and is related to the X-class solar flare. We further found that most of magnetic twists are not released even after the flare, which is consistent with the fact that no observational evidence for major eruptions was found. On the other hand, the upper part of the flux tube is beyond a critical decay index, essential for the excitation of torus instability before the flare, even though no coronal mass ejections were observed. We discuss the stability of the complicated flux tube system and suggest the reason for the existence of the stable flux tube. In addition, we further point out a possibility for tracing the shape of flare ribbons, on the basis of a detailed structural analysis of the NLFFF before a flare.

    DOI: 10.3847/0004-637X/818/2/168

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  49. Fast magnetic reconnection supported by sporadic small-scale Petschek-type shocks Reviewed

    Takuya Shibayama, Kanya Kusano, Takahiro Miyoshi, Takashi Nakabou, Grigory Vekstein

    PHYSICS OF PLASMAS   Vol. 22 ( 10 ) page: id.100706   2015.10

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    Standard magnetohydrodynamic (MHD) theory predicts reconnection rate that is far too slow to account for a wide variety of reconnection events observed in space and laboratory plasmas. Therefore, it was commonly accepted that some non-MHD (kinetic) effects play a crucial role in fast reconnection. A recently renewed interest in simple MHD models is associated with the so-called plasmoid instability of reconnecting current sheets. Although it is now evident that this effect can significantly enhance the rate of reconnection, many details of the underlying multiple-plasmoid process still remain controversial. Here, we report results of a high-resolution computer simulation which demonstrate that fast albeit intermittent magnetic reconnection is sustained by numerous small-scale Petschek-type shocks spontaneously formed in the current sheet due to its plasmoid instability. (C) 2015 Author(s).

    DOI: 10.1063/1.4934652

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  50. Nonlinear regimes of forced magnetic reconnection Reviewed

    G. Vekstein, K. Kusano

    PHYSICS OF PLASMAS   Vol. 22 ( 9 ) page: 090707   2015.9

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    This letter presents a self-consistent description of nonlinear forced magnetic reconnection in Taylor's model of this process. If external boundary perturbation is strong enough, nonlinearity in the current sheet evolution becomes important before resistive effects come into play. This terminates the current sheet shrinking that takes place at the linear stage and brings about its nonlinear equilibrium with a finite thickness. Then, in theory, this equilibrium is destroyed by a finite plasma resistivity during the skin-time, and further reconnection proceeds in the Rutherford regime. However, realization of such a scenario is unlikely because of the plasmoid instability, which is fast enough to develop before the transition to the Rutherford phase occurs. The suggested analytical theory is entirely different from all previous studies and provides proper interpretation of the presently available numerical simulations of nonlinear forced magnetic reconnection. (C) 2015 AIP Publishing LLC.

    DOI: 10.1063/1.4932079

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  51. No Major Solar Flares but the Largest Geomagnetic Storm in the Present Solar Cycle Reviewed

    Y. Kamide, K. Kusano

    SPACE WEATHER-THE INTERNATIONAL JOURNAL OF RESEARCH AND APPLICATIONS   Vol. 13 ( 6 ) page: 365 - 367   2015.6

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    DOI: 10.1002/2015SW001213

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  52. 23pBH-11 Dynamical Petschek Reconnection : New Mechanism of Fast Magnetic Reconnection

    Shibayama T., Kusano K., Miyoshi T., Nakabou T., Vekstein Grigory

    Meeting Abstracts of the Physical Society of Japan   Vol. 70   page: 896 - 896   2015

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    DOI: 10.11316/jpsgaiyo.70.1.0_896

    CiNii Books

  53. Comparison between Hinode/SOT and SDO/HMI, AIA data for the study of the solar flare trigger process Reviewed

    Yumi Bamba, Kanya Kusano, Shinsuke Imada, Yusuke Iida

    PUBLICATIONS OF THE ASTRONOMICAL SOCIETY OF JAPAN   Vol. 66   2014.12

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    Understanding the mechanism that produces solar flares is important not only from the scientific point of view but also for improving space weather predictability. There are numerous observational and computational studies that have attempted to reveal the onset mechanism of solar flares. However, the underlying mechanism of flare onset remains elusive. To elucidate the flare trigger mechanism, we analyzed several flare events which were observed by Hinode/Solar Optical Telescope (SOT) in our previous study. Because of the limitation of the SOT field of view, however, only four events in the Hinode data sets have been usable. Therefore, increasing the number of events is required for evaluating the flare trigger models. We investigated the applicability of data obtained by the Solar Dynamics Observatory (SDO) to increase the data sample for a statistical analysis of the flare trigger process. SDO regularly observes the full disk of the sun and all flares, although its spatial resolution is lower than that of Hinode. We investigated the M6.6 flare which occurred on 2011 February 13, and compared the analyzed data of SDO with the results of our previous study using Hinode/SOT data. Filter and vector magnetograms obtained by the Helioseismic and Magnetic Imager and filtergrams from the Atmospheric Imaging Assembly (AIA) 1600 angstrom were employed. From the comparison of small-scale magnetic configurations and chromospheric emission prior to the flare onset, we confirmed that the trigger region is detectable with the SDO data. We also measured the magnetic shear angles of the active region and the azimuth and strength of the flare trigger field. The results were consistent with our previous study. We concluded that statistical studies of the flare trigger process are feasible with SDO as well as Hinode data. We also investigated the temporal evolution of the magnetic field before the flare onset with SDO.

    DOI: 10.1093/pasj/psu091

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  54. Coronal behavior before the large flare onset Reviewed

    Imada, Shinsuke, Bamba, Yumi, and Kusano, Kanya

    Publ. Astron. Soc. Japan     2014.11

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    DOI: 10.1093/pasj/psu092

  55. Comparison between Hinode/SOT and SDO/HMI, AIA Data for the Study of the Solar Flare Trigger Process Reviewed

    Bamba, Yumi; Kusano, Kanya; Imada, Shinsuke; Iida, Yusuke

    Publications of the Astronomical Society of Japan   Vol. 66 ( SP1 ) page: S1 11   2014.11

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    DOI: 10.1093/pasj/psu092

  56. Formation of a Flare-Productive Active Region: Observation and Numerical Simulation of NOAA AR 11158 Reviewed

    S. Toriumi, Y. Iida, K. Kusano, Y. Bamba, S. Imada

    SOLAR PHYSICS   Vol. 289 ( 9 ) page: 3351 - 3369   2014.9

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    We present a comparison of the Solar Dynamics Observatory (SDO) analysis of NOAA Active Region (AR) 11158 and numerical simulations of flux-tube emergence, aiming to investigate the formation process of this flare-productive AR. First, we use SDO/Helioseismic and Magnetic Imager (HMI) magnetograms to investigate the photospheric evolution and Atmospheric Imaging Assembly (AIA) data to analyze the relevant coronal structures. Key features of this quadrupolar region are a long sheared polarity inversion line (PIL) in the central delta-sunspots and a coronal arcade above the PIL. We find that these features are responsible for the production of intense flares, including an X2.2-class event. Based on the observations, we then propose two possible models for the creation of AR 11158 and conduct flux-emergence simulations of the two cases to reproduce this AR. Case 1 is the emergence of a single flux tube, which is split into two in the convection zone and emerges at two locations, while Case 2 is the emergence of two isolated but neighboring tubes. We find that, in Case 1, a sheared PIL and a coronal arcade are created in the middle of the region, which agrees with the AR 11158 observation. However, Case 2 never builds a clear PIL, which deviates from the observation. Therefore, we conclude that the flare-productive AR 11158 is, between the two cases, more likely to be created from a single split emerging flux than from two independent flux bundles.

    DOI: 10.1007/s11207-014-0502-1

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  57. NONLINEAR FORCE-FREE EXTRAPOLATION OF THE CORONAL MAGNETIC FIELD BASED ON THE MAGNETOHYDRODYNAMIC RELAXATION METHOD Reviewed

    S. Inoue, T. Magara, V. S. Pandey, D. Shiota, K. Kusano, G. S. Choe, K. S. Kim

    ASTROPHYSICAL JOURNAL   Vol. 780 ( 1 ) page: 101   2014.1

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    We develop a nonlinear force-free field (NLFFF) extrapolation code based on the magnetohydrodynamic (MHD) relaxation method. We extend the classical MHD relaxation method in two important ways. First, we introduce an algorithm initially proposed by Dedner et al. to effectively clean the numerical errors associated with del . B. Second, the multigrid type method is implemented in our NLFFF to perform direct analysis of the high-resolution magnetogram data. As a result of these two implementations, we successfully extrapolated the high resolution force-free field introduced by Low & Lou with better accuracy in a drastically shorter time. We also applied our extrapolation method to the MHD solution obtained from the flux-emergence simulation by Magara. We found that NLFFF extrapolation may be less effective for reproducing areas higher than a half-domain, where some magnetic loops are found in a state of continuous upward expansion. However, an inverse S-shaped structure consisting of the sheared and twisted loops formed in the lower region can be captured well through our NLFFF extrapolation method. We further discuss how well these sheared and twisted fields are reconstructed by estimating the magnetic topology and twist quantitatively.

    DOI: 10.1088/0004-637X/780/1/101

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  58. A Plasma β Transition within a Propagating Flux Rope Reviewed

    Savani, N. P., Vourlidas, A., Shiota, D., Linton, M. G., Kusano, K., Lugaz, N., Rouillard, A. P.

    The Astrophysical Journal   Vol. 779 ( 2 ) page: 142   2013.12

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  59. A PLASMA beta TRANSITION WITHIN A PROPAGATING FLUX ROPE Reviewed

    N. P. Savani, A. Vourlidas, D. Shiota, M. G. Linton, K. Kusano, N. Lugaz, A. P. Rouillard

    ASTROPHYSICAL JOURNAL   Vol. 779 ( 2 )   2013.12

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    We present a 2.5 dimensional magnetohydrodynamic simulation of a magnetic flux rope (FR) propagating in the heliosphere and investigate the cause of the observed sharp plasma beta transition. Specifically, we consider a strong internal magnetic field and an explosive fast start, such that the plasma beta is significantly lower in the FR than in the sheath region that is formed ahead. This leads to an unusual FR morphology in the first stage of propagation, while the more traditional view (e. g., from space weather simulations like Enlil) of a pancake-shaped FR is observed as it approaches 1 AU. We investigate how an equipartition line, defined by a magnetic Weber number, surrounding a core region of a propagating FR, can demarcate a boundary layer where there is a sharp transition in the plasma beta. The substructure affects the distribution of toroidal flux, with the majority of the flux remaining in a small core region that maintains a quasi-cylindrical structure. We quantitatively investigate a locus of points where the kinetic energy density of the relative inflow field is equal to the energy density of the transverse magnetic field (i.e., effective tension force). The simulation provides compelling evidence that at all heliocentric distances the distribution of toroidal magnetic flux away from the FR axis is not linear, with 80% of the toroidal flux occurring within 40% of the distance from the FR axis. Thus, our simulation displays evidence that the competing ideas of a pancaking structure observed remotely can coexist with a quasi-cylindrical magnetic structure seen in situ.

    DOI: 10.1088/0004-637X/779/2/142

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  60. Study on Triggering Process of Solar Flares Based on Hinode/SOT Observations Reviewed

    Bamba, Y., Kusano, K., Yamamoto, T. T., Okamoto, T. J.

    The Astrophysical Journal   Vol. 778 ( 1 ) page: 48   2013.11

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  61. Study of Magnetic Helicity Injection in the Active Regions NOAA 9236 Producing Multiple Flare-associated CME Events

    Park, S., Kusano, K., Cho, K, Chae, J., Bong, S., Kumar, P., Park, S., Kim, Y., Park, Y.

    The Astrophysical Journal   Vol. 778 ( 1 ) page: 13   2013.11

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  62. STUDY OF MAGNETIC HELICITY INJECTION IN THE ACTIVE REGION NOAA 9236 PRODUCING MULTIPLE FLARE-ASSOCIATED CORONAL MASS EJECTION EVENTS Reviewed

    Sung-Hong Park, Kanya Kusano, Kyung-Suk Cho, Jongchul Chae, Su-Chan Bong, Pankaj Kumar, So-Young Park, Yeon-Han Kim, Young-Deuk Park

    ASTROPHYSICAL JOURNAL   Vol. 778 ( 1 )   2013.11

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    To better understand a preferred magnetic field configuration and its evolution during coronal mass ejection (CME) events, we investigated the spatial and temporal evolution of photospheric magnetic fields in the active region NOAA 9236 that produced eight flare-associated CMEs during the time period of 2000 November 23-26. The time variations of the total magnetic helicity injection rate and the total unsigned magnetic flux are determined and examined not only in the entire active region but also in some local regions such as the main sunspots and the CME-associated flaring regions using SOHO/MDI magnetogram data. As a result, we found that (1) in the sunspots, a large amount of positive (right-handed) magnetic helicity was injected during most of the examined time period, (2) in the flare region, there was a continuous injection of negative (left-handed) magnetic helicity during the entire period, accompanied by a large increase of the unsigned magnetic flux, and (3) the flaring regions were mainly composed of emerging bipoles of magnetic fragments in which magnetic field lines have substantially favorable conditions for making reconnection with large-scale, overlying, and oppositely directed magnetic field lines connecting the main sunspots. These observational findings can also be well explained by some MHD numerical simulations for CME initiation (e. g., reconnection-favored emerging flux models). We therefore conclude that reconnection-favored magnetic fields in the flaring emerging flux regions play a crucial role in producing the multiple flare-associated CMEs in NOAA 9236.

    DOI: 10.1088/0004-637X/778/1/13

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  63. STUDY ON THE TRIGGERING PROCESS OF SOLAR FLARES BASED ON HINODE/SOT OBSERVATIONS Reviewed

    Y. Bamba, K. Kusano, T. T. Yamamoto, T. J. Okamoto

    ASTROPHYSICAL JOURNAL   Vol. 778 ( 1 )   2013.11

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    We investigated four major solar flare events that occurred in active regions NOAA 10930 (2006 December 13 and 14) and NOAA 11158 (2011 February 13 and 15) by using data observed by the Solar Optical Telescope on board the Hinode satellite. To reveal the trigger mechanism of solar flares, we analyzed the spatio-temporal correlation between the detailed magnetic field structure and the emission image of the Ca ii H line at the central part of flaring regions for several hours prior to the onset of the flares. In all the flare events, we observed that the magnetic shear angle in the flaring regions exceeded 70 degrees, as well as that characteristic magnetic disturbances developed at the centers of flaring regions in the pre-flare phase. These magnetic disturbances can be classified into two groups depending on the structure of their magnetic polarity inversion lines; the so-called opposite-polarity and reversed-shear magnetic field recently proposed by our group, although the magnetic disturbance in one event of the four samples is too subtle to clearly recognize the detailed structure. The result suggests that some major solar flares are triggered by rather small magnetic disturbances. We also show that the critical size of the flare-trigger field varies among flare events and briefly discuss how the flare-trigger process depends on the evolution of active regions.

    DOI: 10.1088/0004-637X/778/1/48

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  64. Onset of Hall-mediated magnetic reconnection in weakly ionized astrophysical plasmas Reviewed

    Vekstein, G. and Kusano, K.

    Monthly Notices of the Royal Astronomical Society   Vol. 434   page: 1789-1791   2013.9

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  65. Onset of Hall-mediated magnetic reconnection in weakly ionized astrophysical plasmas Reviewed

    Grigory Vekstein, Kanya Kusano

    MONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY   Vol. 434 ( 2 ) page: 1789 - 1791   2013.9

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    We consider transition to Hall-magnetohydrodynamics regimes of the resistive tearing instability in weakly ionized plasmas. A particular emphasis is put on a possible role of the resulting fast magnetic reconnection in such astrophysical objects as solar chromosphere, interstellar molecular clouds and protostellar discs. It is shown that Hall-mediated reconnection can be relevant to explosive phenomena in the latter, though it is unlikely to take place in the former two environments.

    DOI: 10.1093/mnras/stt1155

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  66. Magnetic Systems Triggering the M6.6-class Solar Flare in NOAA Active Region 11158 Reviewed

    Toriumi, S., Iida, Y., Bamba, Y., Kusano, K., Imada, S., Satoshi Inoue

    The Astrophysical Journal   Vol. 773 ( 2 ) page: 128   2013.8

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  67. THE MAGNETIC SYSTEMS TRIGGERING THE M6.6 CLASS SOLAR FLARE IN NOAA ACTIVE REGION 11158 Reviewed

    Shin Toriumi, Yusuke Iida, Yumi Bamba, Kanya Kusano, Shinsuke Imada, Satoshi Inoue

    ASTROPHYSICAL JOURNAL   Vol. 773 ( 2 )   2013.8

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    We report a detailed event analysis of the M6.6 class flare in the active region (AR) NOAA 11158 on 2011 February 13. AR 11158, which consisted of two major emerging bipoles, showed prominent activity including one X- and several M-class flares. In order to investigate the magnetic structures related to the M6.6 event, particularly the formation process of a flare-triggering magnetic region, we analyzed multiple spacecraft observations and numerical results of a flare simulation. We observed that, in the center of this quadrupolar AR, a highly sheared polarity inversion line (PIL) was formed through proper motions of the major magnetic elements, which built a sheared coronal arcade lying over the PIL. The observations lend support to the interpretation that the target flare was triggered by a localized magnetic region that had an intrusive structure, namely, a positive polarity penetrating into a negative counterpart. The geometrical relationship between the sheared coronal arcade and the triggering region is consistent with the theoretical flare model based on the previous numerical study. We found that the formation of the trigger region was due to the continuous accumulation of small-scale magnetic patches. A few hours before the flare occurred, the series of emerged/advected patches reconnected with a pre-existing field. Finally, the abrupt flare eruption of the M6.6 event started around 17:30 UT. Our analysis suggests that in the process of triggering flare activity, all magnetic systems on multiple scales are included, not only the entire AR evolution but also the fine magnetic elements.

    DOI: 10.1088/0004-637X/773/2/128

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  68. Is Something Wrong With the Present Solar Maximum? Reviewed

    Y. Kamide, K. Kusano

    SPACE WEATHER-THE INTERNATIONAL JOURNAL OF RESEARCH AND APPLICATIONS   Vol. 11 ( 4 ) page: 140 - 141   2013.4

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    DOI: 10.1002/swe.20045

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  69. Comment on "Supersonic regime of the Hall-magnetohydrodynamics resistive tearing instability" [Phys. Plasmas 19, 072519 (2012)] Reviewed

    G. Vekstein, K. Kusano

    PHYSICS OF PLASMAS   Vol. 20 ( 1 ) page: 014703-014703-2   2013.1

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    Ahedo and Ramos [Phys. Plasmas 19, 072519 (2012)] revisited what they called the supersonic regime of the Hall-mediated resistive tearing instability and arrived to results that disagree with the previously known ones (Fruchtman and Strauss [Phys. Fluids B 5, 1408 (1993)], Bian and Vekstein [Phys. Plasmas 14, 072107 (2007)]). The present Comment aims to clarify the origin of this disagreement and to confirm in this way the validity of the earlier findings. (C) 2013 American Institute of Physics. [http://dx.doi.org/10.1063/1.4789449]

    DOI: 10.1063/1.4789449

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  70. Guidelines for Non-Pharmacotherapy of Cardiac Arrhythmias (JCS 2011) - Digest Version

    Okumura Ken, Aizawa Yoshifusa, Aonuma Kazutaka, Hagiwara Nobuhisa, Isobe Fumitaka, Katoh Takao, Matsumoto Kazuo, Murakawa Yuji, Nitta Takashi, Ohnishi Satoshi, Shimizu Akihiko, Hirao Kenzo, Ishikawa Toshiyuki, Iwa Toru, Kurita Takashi, Kusano Kengo, Nakamura Yoshihide, Nakazato Yuji, Niwano Shinichi, Sasaki Shingo, Shiga Tsuyoshi, Shoda Morio, Sumitomo Naokata, Umemura Jun, Kasanuki Hiroshi, Kimura Takeshi, Kodama Itsuo, Ohe Tohru, Tanaka Shigeo

    CIRCULATION JOURNAL   Vol. 77 ( 1 ) page: 249-274   2013.1

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    DOI: 10.1253/circj.CJ-66-0054

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  71. MAGNETIC FIELD STRUCTURES TRIGGERING SOLAR FLARES AND CORONAL MASS EJECTIONS Reviewed

    K. Kusano, Y. Bamba, T. T. Yamamoto, Y. Iida, S. Toriumi, A. Asai

    ASTROPHYSICAL JOURNAL   Vol. 760 ( 1 ) page: article id 31.9   2012.11

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    Solar flares and coronal mass ejections, the most catastrophic eruptions in our solar system, have been known to affect terrestrial environments and infrastructure. However, because their triggering mechanism is still not sufficiently understood, our capacity to predict the occurrence of solar eruptions and to forecast space weather is substantially hindered. Even though various models have been proposed to determine the onset of solar eruptions, the types of magnetic structures capable of triggering these eruptions are still unclear. In this study, we solved this problem by systematically surveying the nonlinear dynamics caused by a wide variety of magnetic structures in terms of three-dimensional magnetohydrodynamic simulations. As a result, we determined that two different types of small magnetic structures favor the onset of solar eruptions. These structures, which should appear near the magnetic polarity inversion line (PIL), include magnetic fluxes reversed to the potential component or the nonpotential component of major field on the PIL. In addition, we analyzed two large flares, the X-class flare on 2006 December 13 and the M-class flare on 2011 February 13, using imaging data provided by the Hinode satellite, and we demonstrated that they conform to the simulation predictions. These results suggest that forecasting of solar eruptions is possible with sophisticated observation of a solar magnetic field, although the lead time must be limited by the timescale of changes in the small magnetic structures.

    DOI: 10.1088/0004-637X/760/1/31

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  72. A STUDY OF THE HELIOCENTRIC DEPENDENCE OF SHOCK STANDOFF DISTANCE AND GEOMETRY USING 2.5D MAGNETOHYDRODYNAMIC SIMULATIONS OF CORONAL MASS EJECTION DRIVEN SHOCKS Reviewed

    N. P. Savani, D. Shiota, K. Kusano, A. Vourlidas, N. Lugaz

    ASTROPHYSICAL JOURNAL   Vol. 759 ( 2 ) page: artiticle id. 103.11   2012.11

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    We perform four numerical magnetohydrodynamic simulations in 2.5 dimensions ( 2.5D) of fast coronal mass ejections (CMEs) and their associated shock fronts between 10 Rs and 300 Rs. We investigate the relative change in the shock standoff distance, Delta, as a fraction of the CME radial half-width, D-OB (i.e., Delta/D-OB). Previous hydrodynamic studies have related the shock standoff distance for Earth's magnetosphere to the density compression ratio (DR; rho(u)/rho(d)) measured across the bow shock. The DR coefficient, k(dr), which is the proportionality constant between the relative standoff distance (Delta/D-OB) and the compression ratio, was semi-empirically estimated as 1.1. For CMEs, we show that this value varies linearly as a function of heliocentric distance and changes significantly for different radii of curvature of the CME's leading edge. We find that a value of 0.8 +/- 0.1 is more appropriate for small heliocentric distances (&lt;30 Rs) which corresponds to the spherical geometry of a magnetosphere presented by Seiff. As the CME propagates its cross section becomes more oblate and the k(dr) value increases linearly with heliocentric distance, such that k(dr) = 1.1 is most appropriate at a heliocentric distance of about 80 Rs. For terrestrial distances (215 Rs) we estimate k(dr) = 1.8 +/- 0.3, which also indicates that the CME cross-sectional structure is generally more oblate than that of Earth's magnetosphere. These alterations to the proportionality coefficients may serve to improve investigations into the estimates of the magnetic field in the corona upstream of a CME as well as the aspect ratio of CMEs as measured in situ.

    DOI: 10.1088/0004-637X/759/2/103

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  73. Observational Tracking of the 2D Structure of Coronal Mass Ejections Between the Sun and 1 AU Reviewed

    N. P. Savani, J. A. Davies, C. J. Davis, D. Shiota, A. P. Rouillard, M. J. Owens, K. Kusano, V. Bothmer, S. P. Bamford, C. J. Lintott, A. Smith

    SOLAR PHYSICS   Vol. 279 ( 2 ) page: 517 - 535   2012.8

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    The Solar TErrestrial RElations Observatory (STEREO) provides high cadence and high resolution images of the structure and morphology of coronal mass ejections (CMEs) in the inner heliosphere. CME directions and propagation speeds have often been estimated through the use of time-elongation maps obtained from the STEREO Heliospheric Imager (HI) data. Many of these CMEs have been identified by citizen scientists working within the SolarStormWatch project (www.solarstormwatch.com) as they work towards providing robust real-time identification of Earth-directed CMEs. The wide field of view of HI allows scientists to directly observe the two-dimensional (2D) structures, while the relative simplicity of time-elongation analysis means that it can be easily applied to many such events, thereby enabling a much deeper understanding of how CMEs evolve between the Sun and the Earth. For events with certain orientations, both the rear and front edges of the CME can be monitored at varying heliocentric distances (R) between the Sun and 1 AU. Here we take four example events with measurable position angle widths and identified by the citizen scientists. These events were chosen for the clarity of their structure within the HI cameras and their long track lengths in the time-elongation maps. We show a linear dependency with R for the growth of the radial width (W) and the 2D aspect ratio (.) of these CMEs, which are measured out to approximate to 0.7 AU. We estimated the radial width from a linear best fit for the average of the four CMEs. We obtained the relationships W = 0.14R + 0.04 for the width and chi = 2.5R + 0.86 for the aspect ratio (W and R in units of AU).

    DOI: 10.1007/s11207-012-0041-6

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  74. PREPROCESSING MAGNETIC FIELDS WITH CHROMOSPHERIC LONGITUDINAL FIELDS Reviewed

    Tetsuya T. Yamamoto, K. Kusano

    ASTROPHYSICAL JOURNAL   Vol. 752 ( 2 ) page: article id. 126   2012.6

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    Nonlinear force-free field (NLFFF) extrapolation is a powerful tool for the modeling of the magnetic field in the solar corona. However, since the photospheric magnetic field does not in general satisfy the force-free condition, some kind of processing is required to assimilate data into the model. In this paper, we report the results of new preprocessing for the NLFFF extrapolation. Through this preprocessing, we expect to obtain magnetic field data similar to those in the chromosphere. In our preprocessing, we add a new term concerning chromospheric longitudinal fields into the optimization function proposed by Wiegelmann et al. We perform a parameter survey of six free parameters to find minimum force-and torque-freeness with the simulated-annealing method. Analyzed data are a photospheric vector magnetogram of AR 10953 observed with the Hinode spectropolarimeter and a chromospheric longitudinal magnetogram observed with SOLIS spectropolarimeter. It is found that some preprocessed fields show the smallest force-and torque-freeness and are very similar to the chromospheric longitudinal fields. On the other hand, other preprocessed fields show noisy maps, although the force-and torque-freeness are of the same order. By analyzing preprocessed noisy maps in the wave number space, we found that small and large wave number components balance out on the force-free index. We also discuss our iteration limit of the simulated-annealing method and magnetic structure broadening in the chromosphere.

    DOI: 10.1088/0004-637X/752/2/126

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  75. DECORRELATION TIMES OF PHOTOSPHERIC FIELDS AND FLOWS Reviewed

    B. T. Welsch, K. Kusano, T. T. Yamamoto, K. Muglach

    ASTROPHYSICAL JOURNAL   Vol. 747 ( 2 ) page: article id. 130   2012.3

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    We use autocorrelation to investigate evolution in flow fields inferred by applying Fourier local correlation tracking (FLCT) to a sequence of high-resolution (0 ''.3), high-cadence (similar or equal to 2 minute) line-of-sight magnetograms of NOAA active region (AR) 10930 recorded by the narrowband filter imager of the Solar Optical Telescope aboard the Hinode satellite over 2006 December 12 and 13. To baseline the timescales of flow evolution, we also autocorrelated the magnetograms, at several spatial binnings, to characterize the lifetimes of active region magnetic structures versus spatial scale. Autocorrelation of flow maps can be used to optimize tracking parameters, to understand tracking algorithms' susceptibility to noise, and to estimate flow lifetimes. Tracking parameters varied include: time interval Delta t between magnetogram pairs tracked, spatial binning applied to the magnetograms, and windowing parameter sigma used in FLCT. Flow structures vary over a range of spatial and temporal scales (including unresolved scales), so tracked flows represent a local average of the flow over a particular range of space and time. We define flow lifetime to be the flow decorrelation time, tau. For Delta t &gt; tau, tracking results represent the average velocity over one or more flow lifetimes. We analyze lifetimes of flow components, divergences, and curls as functions of magnetic field strength and spatial scale. We find a significant trend of increasing lifetimes of flow components, divergences, and curls with field strength, consistent with Lorentz forces partially governing flows in the active photosphere, as well as strong trends of increasing flow lifetime and decreasing magnitudes with increases in both spatial scale and Delta t.

    DOI: 10.1088/0004-637X/747/2/130

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  76. Fine Structure in Three Dimensional Magnetic Field in Polar Region Reviewed

    Daikou Shiota, Saku Tsuneta, Hiroaki Ito, Kanya Kusano, Noriaki Nishikawa, Takeru K. Suzuki

    HINODE-3: THE 3RD HINODE SCIENCE MEETING   Vol. 454   page: 375 - +   2012

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    In order to discuss the propagation of Alfven wave in the real solar atmosphere, we calculate three dimensional magnetic field using magnetic field observation obtained with Hinode and a high resolution potential field model. The modeled field reproduces fun out (canopy) structure rooted to patchy concentrations of magnetic flux (kG-patches) in the polar region. Combined with a atmosphere model, the model shows that most of the Alfven wave propagating along the magnetic field lines can hardly pass through the transition region due to reflection there. The model suggests that strong concentration of the magnetic field may make retardation of Alfven wave phase between neighboring field lines rooted on the edge of the canopy. The situation may be potential situation for Alfven wave dissipation due to phase mixing process.

    Web of Science

  77. Photospheric Magnetic Motions and a Flare Trigger Mechanism on AR 10930 Reviewed

    Tetsuya T. Yamamoto, K. Kusano

    HINODE-3: THE 3RD HINODE SCIENCE MEETING   Vol. 454   page: 307 - 310   2012

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    In this paper we report shear motions (3-5 km s(-1)) of magnetic elements observed at a preflare of an X3.4 flare (around 02:00 UT on 2006 December 13) in active region 10930. This preflare is observed by X-ray Telescope onboard Hinode. Velocity fields are obtained from filter magnetograms of the Solar Optical Telescope. We also analyzed velocity fields divided into divergent and rotation components. From these velocity components, two local twisting motions are found. One twisting motion continues for 0.5 hours, and another continues at least for 2.5 hours.

    Web of Science

  78. Fine Structure in Three Dimensional Magnetic Field in Polar Region

    Shiota Daikou, Tsuneta Saku, Ito Hiroaki, Kusano Kanya, Nishikawa Noriaki, Suzuki Takeru K.

    HINODE-3: THE 3RD HINODE SCIENCE MEETING   Vol. 454   page: 375 - +   2012

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  79. Photospheric Magnetic Motions and a Flare Trigger Mechanism on AR 10930

    Yamamoto Tetsuya T., Kusano K.

    HINODE-3: THE 3RD HINODE SCIENCE MEETING   Vol. 454   page: 307 - 310   2012

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  80. TWIST AND CONNECTIVITY OF MAGNETIC FIELD LINES IN THE SOLAR ACTIVE REGION NOAA 10930 Reviewed

    S. Inoue, K. Kusano, T. Magara, D. Shiota, T. T. Yamamoto

    ASTROPHYSICAL JOURNAL   Vol. 738 ( 2 )   2011.9

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    Twist and connectivity of magnetic field lines in the flare-productive active region NOAA 10930 are investigated in terms of the vector magnetograms observed by the Solar Optical Telescope on board the Hinode satellite and the nonlinear force-free field (NLFFF) extrapolation. First, we show that the footpoints of magnetic field lines reconstructed by the NLFFF correspond well to the conjugate pair of highly sheared flare ribbons on the Ca II images, which were observed by Hinode as an X3.4 class flare on 2006 December 13. This demonstrates that the NLFFF extrapolation may be used to analyze the magnetic field connectivity. Second, we find that the twist of magnetic field lines anchored on the flare ribbons increased as the ribbons moved away from the magnetic polarity inversion line in the early phase of the flare. This suggests that magnetic reconnection might commence from a region located below the most strongly twisted field. Third, we reveal that the magnetic flux twisted more than a half turn and gradually increased during the last one day prior to the onset of the flare, and that it quickly decreased for two hours after the flare. This is consistent with the store-and-release scenario of magnetic helicity. However, within this active region, only a small fraction of the flux was twisted by more than one full turn and the field lines that reconnected first were twisted less than one turn. These results imply that the kink mode instability could hardly occur, at least before the onset of flare. Based on our results, we discuss the trigger process of solar flares.

    DOI: 10.1088/0004-637X/738/2/161

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  81. CORONAL ELECTRON DISTRIBUTION IN SOLAR FLARES: DRIFT-KINETIC MODEL Reviewed

    Takashi Minoshima, Satoshi Masuda, Yoshizumi Miyoshi, Kanya Kusano

    ASTROPHYSICAL JOURNAL   Vol. 732 ( 2 )   2011.5

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    Using a model of particle acceleration and transport in solar flares, we investigate the height distribution of coronal electrons by focusing on the energy-dependent pitch-angle scattering. When pitch-angle scattering is not included, the peak heights of loop-top electrons are constant, regardless of their energy, owing to the continuous acceleration and compression of the electrons via shrinkage of magnetic loops. On the other hand, under pitch-angle scattering, the electron heights are energy-dependent: intermediate-energy electrons are at a higher altitude, whereas lower and higher energy electrons are at lower altitudes. This implies that the intermediate-energy electrons are inhibited from following the shrinking field lines to lower altitudes because pitch-angle scattering causes efficient precipitation of these electrons into the footpoint and their subsequent loss from the loop. This result is qualitatively consistent with the position of the above-the-loop-top hard X-ray (HXR) source that is located above coronal HXR loops emitted by lower energy electrons and microwaves emitted by higher energy electrons. Quantitative agreement with observations might be achieved by considering primary acceleration before the onset of loop shrinkage and additional pitch-angle scattering via wave-particle interactions.

    DOI: 10.1088/0004-637X/732/2/111

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  82. EVOLUTION OF CORONAL MASS EJECTION MORPHOLOGY WITH INCREASING HELIOCENTRIC DISTANCE. II. IN SITU OBSERVATIONS Reviewed

    N. P. Savani, M. J. Owens, A. P. Rouillard, R. J. Forsyth, K. Kusano, D. Shiota, R. Kataoka, L. Jian, V. Bothmer

    ASTROPHYSICAL JOURNAL   Vol. 732 ( 2 )   2011.5

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    Interplanetary coronal mass ejections (ICMEs) are often observed to travel much faster than the ambient solar wind. If the relative speed between the two exceeds the fast magnetosonic velocity, then a shock wave will form. The Mach number and the shock standoff distance ahead of the ICME leading edge is measured to infer the vertical size of an ICME in a direction that is perpendicular to the solar wind flow. We analyze the shock standoff distance for 45 events varying between 0.5AU and 5.5AU in order to infer their physical dimensions. We find that the average ratio of the inferred vertical size to measured radial width, referred to as the aspect ratio, of an ICME is 2.8 +/- 0.5. We also compare these results to the geometrical predictions from Paper I that forecast an aspect ratio between 3 and 6. The geometrical solution varies with heliocentric distance and appears to provide a theoretical maximum for the aspect ratio of ICMEs. The minimum aspect ratio appears to remain constant at 1 (i.e., a circular cross section) for all distances. These results suggest that possible distortions to the leading edge of ICMEs are frequent. But, these results may also indicate that the constants calculated in the empirical relationship correlating the different shock front need to be modified; or perhaps both distortions and a change in the empirical formulae are required.

    DOI: 10.1088/0004-637X/732/2/117

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  83. EVOLUTION OF CORONAL MASS EJECTION MORPHOLOGY WITH INCREASING HELIOCENTRIC DISTANCE. I. GEOMETRICAL ANALYSIS Reviewed

    N. P. Savani, M. J. Owens, A. P. Rouillard, R. J. Forsyth, K. Kusano, D. Shiota, R. Kataoka

    ASTROPHYSICAL JOURNAL   Vol. 731 ( 2 )   2011.4

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    At launch, coronal mass ejections (CMEs) are often approximated as locally cylindrical objects with circular cross sections. However, CMEs have long been known to propagate almost radially away from the Sun along with the bulk solar wind. This has important consequences for the structure of CMEs; an initially circular cross section will be severely flattened by this radial motion. Yet calculations of total flux and helicity transport by CMEs based on in situ observations still use the assumption of a locally cylindrical object. In this paper, we investigate the morphology of an interplanetary CME based upon geometric arguments. By radially propagating an initial cylindrical object that maintains a constant ratio between its expansion speed and bulk flow, A, we show that the flattening, or "pancaking," of the two-dimensional cross section effectively ceases; the aspect ratios of these CMEs converge to a fixed value as they propagate further into the heliosphere. Thereafter the CME morphology is scale invariant. We predict aspect ratios of 5 +/- 1 at terrestrial distances. By correlating a planetary shock with an interplanetary shock linked to a CME, these aspect ratios are estimated using in situ measurements in Paper II. These estimates are made at various heliocentric distances.

    DOI: 10.1088/0004-637X/731/2/109

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  84. Discussion on Momentum Transfer Difficulty of Magneto-Plasma Sail Reviewed

    H.Nishida, I. Funaki, Y.Inatani, and K.Kusano

    JOURNAL OF PROPULSION AND POWER   Vol. 27 ( 5 ) page: 1149-1153   2011

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  85. Twist and connectivity of magnetic field lines in the solar active region NOAA 10930 Reviewed

    S. Inoue, K.Kusano, T. Magara, D. Shiota, T. T. Yamamoto

    The Astrophysical Journal   Vol. 738 ( 2 ) page: article id 161   2011

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  86. A comparative study of divergence-cleaning techniques for multi-dimensional MHD schemes Reviewed

    Takahiro Miyoshi, Kanya Kusano

    Plasma and Fusion Research   Vol. 6   page: 2401124(1-5)   2011

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  87. Discussion on Momentum Transfer Difficulty of a Magnetoplasma Sail Reviewed

    Hiroyuki Nishida, Ikkoh Funaki, Yoshifumi Inatani, Kanya Kusano

    JOURNAL OF PROPULSION AND POWER   Vol. 27 ( 5 ) page: 1149 - 1153   2011

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    DOI: 10.2514/1.B34141

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  88. The SOLAR-C mission: current status Reviewed

    Toshifumi Shimizu, Saku Tsuneta, Hirohisa Hara, Kiyoshi Ichimoto, Kanya Kusano, Taro Sakao, Takashi Sekii, Yoshinori Suematsu, Tetsuya Watanabe

    SOLAR PHYSICS AND SPACE WEATHER INSTRUMENTATION IV   Vol. 8148   2011

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    Two mission concepts (plan A: out-of-ecliptic mission and plan B: high resolution spectroscopic mission) have been studied for the next Japanese-led solar mission Solar-C, which will follow the scientific success of the Hinode mission. The both mission concepts are concluded as equally important and attractive for the promotion of space solar physics. In the meantime we also had to make efforts for prioritizing the two options, in order to proceed to next stage of requesting the launch of Solar-C mission at the earliest opportunity. This paper briefly describes the two mission concepts and the current status on our efforts for prioritizing the two options. More details are also described for the plan B option as the first-priority Solar-C mission. The latest report from the Solar-C mission concept studies was documented as "Interim Report on the Solar-C Mission Concept."

    DOI: 10.1117/12.893228

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  89. A Comparative study of divergence-cleaning techniques for multi-dimensional MHD schemes Reviewed

    Takahiro Miyoshi, Kanya Kusano

    Plasma and Fusion Research   Vol. 6 ( 1 ) page: 2401124-1 - 2401124-5   2011

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    Several divergence-cleaning techniques for multi-dimensional Godunov-type magnetohydrodynamic schemes are comparatively investigated. We also propose a new divergence-cleaning technique that is improved from an earlier projection method to improve the robustness. © 2011 The Japan Society of Plasma Science and Nuclear Fusion Research.

    DOI: 10.1585/pfr.6.2406124

    Scopus

  90. The HLLD Approximate Riemann Solver for Magnetospheric Simulation Reviewed

    Takahiro Miyoshi, Naoki Terada, Yosuke Matsumoto, Keiichiro Fukazawa, Takayuki Umeda, Kanya Kusano

    IEEE Transactions on Plasma Science   Vol. 38 ( 9 ) page: 2236-2242   2010.9

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    A magnetohydrodynamic (MHD) algorithm for global simulations of planetary magnetospheres is developed based on an approximate nonlinear Riemann solver, the so-called Harten-Lax-van Leer-Discontinuities (HLLD) approximate Riemann solver. An approximate nonlinear solution of the MHD Riemann problem, in which the contributions of the background potential magnetic field are subtracted and multispecies plasmas as well as general equation of state are included, can be algebraically obtained under the assumptions that the normal velocity and the background potential magnetic field in the Riemann fan are constant. The theoretical aspects of the HLLD approximate Riemann solver are focused on, in particular.

  91. The HLLD Approximate Riemann Solver for Magnetospheric Simulation Reviewed

    Takahiro Miyoshi, Naoki Terada, Yosuke Matsumoto, Keiichiro Fukazawa, Takayuki Umeda, Kanya Kusano

    IEEE TRANSACTIONS ON PLASMA SCIENCE   Vol. 38 ( 9 ) page: 2236 - 2242   2010.9

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    A magnetohydrodynamic (MHD) algorithm for global simulations of planetary magnetospheres is developed based on an approximate nonlinear Riemann solver, the so-called Harten-Lax-van Leer-Discontinuities (HLLD) approximate Riemann solver. An approximate nonlinear solution of the MHD Riemann problem, in which the contributions of the background potential magnetic field are subtracted and multispecies plasmas as well as general equation of state are included, can be algebraically obtained under the assumptions that the normal velocity and the background potential magnetic field in the Riemann fan are constant. The theoretical aspects of the HLLD approximate Riemann solver are focused on, in particular.

    DOI: 10.1109/TPS.2010.2057451

    Web of Science

  92. MAGNETOHYDRODYNAMIC MODELING FOR A FORMATION PROCESS OF CORONAL MASS EJECTIONS: INTERACTION BETWEEN AN EJECTING FLUX ROPE AND AN AMBIENT FIELD Reviewed

    Daikou Shiota, Kanya Kusano, Takahiro Miyoshi, Kazunari Shibata

    ASTROPHYSICAL JOURNAL   Vol. 718 ( 2 ) page: 1305 - 1314   2010.8

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    We performed a magnetohydrodynamic simulation of a formation process of coronal mass ejections (CMEs), focusing on the interaction (reconnection) between an ejecting flux rope and its ambient field. We examined three cases with different ambient fields: one had no ambient field, while the other two had dipole fields with opposite directions, parallel and anti-parallel to that of the flux rope surface. We found that while the flux rope disappears in the anti-parallel case, in the other cases the flux ropes can evolve to CMEs and show different amounts of flux rope rotation. The results imply that the interaction between an ejecting flux rope and its ambient field is an important process for determining CME formation and CME orientation, and also show that the amount and direction of the magnetic flux within the flux rope and the ambient field are key parameters for CME formation. The interaction (reconnection) plays a significant role in the rotation of the flux rope especially with a process similar to "tilting instability" in a spheromak-type experiment of laboratory plasma.

    DOI: 10.1088/0004-637X/718/2/1305

    Web of Science

  93. MHD modeling for Formation Process of Coronal Mass Ejections:Interaction between Ejecting Flux Rope and Ambient Field Reviewed

    Daikou Shiota, Kanya Kusano, Takahiro Miyoshi, Kazunari Shibata

    The Astrophysical Journal   Vol. 718 ( 2 ) page: 1305-1314   2010.8

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    Language:English   Publishing type:Research paper (scientific journal)  

    We performed a magnetohydrodynamic simulation of a formation process of coronal mass ejections (CMEs), focusing on the interaction (reconnection) between an ejecting flux rope and its ambient field. We examined three cases with different ambient fields: one had no ambient field, while the other two had dipole fields with opposite directions, parallel and anti-parallel to that of the flux rope surface. We found that while the flux rope disappears in the anti-parallel case, in the other cases the flux ropes can evolve to CMEs and show different amounts of flux rope rotation. The results imply that the interaction between an ejecting flux rope and its ambient field is an important process for determining CME formation and CME orientation, and also show that the amount and direction of the magnetic flux within the flux rope and the ambient field are key parameters for CME formation. The interaction (reconnection) plays a significant role in the rotation of the flux rope especially with a process similar to "tilting instability" in a spheromak-type experiment of laboratory plasma.

  94. *Three-dimensional MHD modeling of the solar wind structures associated with 13 December 2006 coronal mass ejection Reviewed

    Kataoka R, Ebisuzaki T, Kusano K, Shiota D, Inoue S, Yamamoto TT, Tokumaru M

    JOURNAL OF GEOPHYSICAL RESEARCH-SPACE PHYSICS   Vol. 114   page: A10102   2009.10

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    A 3-D magnetohydrodynamic (MHD) simulation is performed to reconstruct the interplanetary propagation of a coronal mass ejection (CME) that occurred on 13 December 2006. A spheromak-type magnetic field is superposed on a realistic ambient solar wind to reproduce the large-scale interplanetary magnetic field (IMF) associated with the CME. Here we show that a westward and southward directed spheromak CME with reasonable geometric, dynamic, and magnetic parameters reproduces the magnetic cloud, interplanetary shock, and sheath profiles as observed by in situ spacecraft. We suggest that the simple solar wind model developed in this study is topologically complex enough to be consistent with in situ observations, such as southward IMF associated with CMEs.

  95. *The super-droplet method for the numerical simulation of clouds and precipitation: A particle-based and probabilistic microphysics model coupled with a non-hydrostatic model Reviewed

    Shima S, Kusano K, Kawano A, Sugiyama T, Kawahara S

    QUARTERLY JOURNAL OF THE ROYAL METEOROLOGICAL   Vol. 135 ( 642 ) page: 1307-1320   2009.7

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    A novel, particle-based, probabilistic approach for the Simulation of cloud microphysics is proposed, which is named the super-droplet method (SDM). This method enables the accurate simulation of cloud microphysics with a less demanding cost in Computation. SDM is applied to a warm-cloud system, which incorporates sedimentation, condensation/evaporation and stochastic coalescence. The methodology to couple super-droplets and a non-hydrostatic model is also developed. It is confirmed that the result of our Monte Carlo scheme for the stochastic coalescence of super-droplets agrees fairly well with the solutions of the stochastic coalescence equation. The behaviour of the model is evaluated using a simple test problem, that of a shallow maritime cumulus formation initiated by a warm bubble. Possible extensions of SDM are briefly discussed. A theoretical analysis suggests that the Computational cost of SDM becomes lower than the spectral (bin) method when the number of attributes - the variables that identify the state of each super-droplet - becomes larger than some critical value, which we estimate to be in the range 2 similar to 4. Copyright (C) 2009 Royal Meteorological Society

  96. The super-droplet method for the numerical simulation of clouds and precipitation: A particle-based and probabilistic microphysics model coupled with a non-hydrostatic model Reviewed

    S. Shima, K. Kusano, A. Kawano, T. Sugiyama, S. Kawahara

    QUARTERLY JOURNAL OF THE ROYAL METEOROLOGICAL SOCIETY   Vol. 135 ( 642 ) page: 1307 - 1320   2009.7

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    Language:English   Publishing type:Research paper (scientific journal)   Publisher:WILEY-BLACKWELL  

    A novel, particle-based, probabilistic approach for the Simulation of cloud microphysics is proposed, which is named the super-droplet method (SDM). This method enables the accurate simulation of cloud microphysics with a less demanding cost in Computation. SDM is applied to a warm-cloud system, which incorporates sedimentation, condensation/evaporation and stochastic coalescence. The methodology to couple super-droplets and a non-hydrostatic model is also developed. It is confirmed that the result of our Monte Carlo scheme for the stochastic coalescence of super-droplets agrees fairly well with the solutions of the stochastic coalescence equation. The behaviour of the model is evaluated using a simple test problem, that of a shallow maritime cumulus formation initiated by a warm bubble. Possible extensions of SDM are briefly discussed. A theoretical analysis suggests that the Computational cost of SDM becomes lower than the spectral (bin) method when the number of attributes - the variables that identify the state of each super-droplet - becomes larger than some critical value, which we estimate to be in the range 2 similar to 4. Copyright (C) 2009 Royal Meteorological Society

    DOI: 10.1002/qj.441

    Web of Science

  97. Three-dimensional MHD modeling of the solar wind structures associated with 13 December 2006 coronal mass ejection Reviewed

    R. Kataoka, T. Ebisuzaki, K. Kusano, D. Shiota, S. Inoue, T. T. Yamamoto, M. Tokumaru

    Journal of Geophysical Research: Space Physics   Vol. 114 ( 10 ) page: 10102   2009

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    Language:English   Publishing type:Research paper (scientific journal)   Publisher:Blackwell Publishing Ltd  

    A 3-D magnetohydrodynamic (MHD) simulation is performed to reconstruct the interplanetary propagation of a coronal mass ejection (CME) that occurred on 13 December 2006. A spheromak-type magnetic field is superposed on a realistic ambient solar wind to reproduce the large-scale interplanetary magnetic field (IMF) associated with the CME. Here we show that a westward and southward directed spheromak CME with reasonable geometric, dynamic, and magnetic parameters reproduces the magnetic cloud, interplanetary shock, and sheath profiles as observed by in situ spacecraft. We suggest that the simple solar wind model developed in this study is topologically complex enough to be consistent with in situ observations, such as southward IMF associated with CMEs. Copyright 2009 by the American Geophysical Union.

    DOI: 10.1029/2009JA014167

    Web of Science

    Scopus

  98. Continuum/particle interlocked simulation of gas detonation Reviewed

    A. Kawano, K. Kusano

    SHOCK WAVES, VOL 1, PROCEEDINGS     page: 215 - 220   2009

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    Language:English   Publishing type:Research paper (international conference proceedings)   Publisher:SPRINGER-VERLAG BERLIN  

    A multiscale simulation method for gas detonations is proposed. This method is performed by the interlocking of a continuum fluid model and a particle based molecular model. The simulation system is spatially divided into the two kinds of domains, in one of which the near-thermal equilibrium is satisfied but not in the other. The dynamics of the near-thermal equilibrium domains is modeled by the continuum fluid dynamic equations. In the nonthermal equilibrium domain, which corresponds to the denotation front, the dynamics is modeled by the Boltzmann equation. This method has been tested on a model detonation system.

    Web of Science

  99. MHD Flow Field and Momentum Transfer Process of Magneto-Plasma Sail

    Hiroyuki Nishida, Ikkoh Funaki, Yoshifumi Inatani, Kanya Kusano

    Journal of Plasma and Fusion Research SERIES   Vol. Vol.8   page: 1574 - 1579   2009

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    Language:English   Publishing type:Research paper (international conference proceedings)  

  100. Simulation study of the symmetry-breaking instability and the dipole field reversal in a rotating spherical shell dynamo Reviewed

    N. Nishikawa, K. Kusano

    PHYSICS OF PLASMAS   Vol. 15 ( 8 )   2008.8

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    Language:English   Publishing type:Research paper (scientific journal)   Publisher:AMER INST PHYSICS  

    The reversal mechanism of a dipole magnetic field generated by dynamo action in a rotating spherical shell is investigated by a three-dimensional nonlinear magnetohydrodynamic simulation as well as a linear stability analysis. The emphasis of the study is on understanding the relationship between dipole reversal and the symmetry properties of the dynamo solution. As a result, first, it is found that there is a threshold of the magnetic Prandtl number, below which the dipole field is never reversed, and above which the reversal occurs at irregular intervals like the paleomagnetic evolution of the geodynamo. Second, it is shown that the dynamo process responsible for the generation of a dipole field (called "a-dynamo" in this paper) consists only of the antimirror symmetric magnetic field and the mirror symmetric velocity field with respect to the equatorial plane. Third, it is found that the components of the opposite symmetry to the a-dynamo grow only during the polarity reversal events and quickly decay afterwards. This indicates that the dipole field reversal and the loss of equatorial symmetry are tightly connected. In fact, it is clearly demonstrated by numerical analyses that the a-dynamo process is linearly unstable for the perturbation of opposite symmetry when the magnetic Prandtl number exceeds the threshold for dipole reversal. Mode coupling between the longitudinal Fourier components plays a crucial role in creating the instability. Based on the above results, it is proposed that symmetry-breaking instability could be the mechanism for dipole field reversal in the geodynamo process. The energy conversion between components of different symmetry is also analyzed in the quasistable polarity phase and in the polarity reversal phase, respectively. (C) 2008 American Institute of Physics.

    DOI: 10.1063/1.2959120

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  101. Tests and comparisons of velocity-inversion techniques (vol 670, pg 1434, 2007) Reviewed

    B. T. Welsch, W. P. Abbett, M. L. DeRosa, G. H. Fisher, M. K. Georgoulis, K. Kusano, D. W. Longcope, B. Ravindra, P. W. Schuck

    ASTROPHYSICAL JOURNAL   Vol. 680 ( 1 ) page: 827 - 827   2008.6

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    Language:English   Publishing type:Research paper (scientific journal)   Publisher:UNIV CHICAGO PRESS  

    DOI: 10.1086/588021

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  102. A quantitative MHD study of the relation among arcade shearing, flux rope formation, and eruption due to the tearing instability Reviewed

    D. Shiota, K. Kusano, T. Miyoshi, N. Nishikawa, K. Shibata

    Journal of Geophysical Research: Space Physics   Vol. 113 ( 3 )   2008.3

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    Language:English   Publishing type:Research paper (international conference proceedings)   Publisher:Blackwell Publishing Ltd  

    The quantitative relationship between the magnetohydrodynamic (MHD) activity of solar coronal arcade and the magnetic helicity injection, which is caused by shearing motion, has been investigated, using azimuthally symmetric model of MHD simulation. We have calculated several cases in which the width of the shearing region is varied and examined the relationship between the magnetic arcade dynamics and magnetic helicity evolution. As a result, it is found that as the shearing motion is imposed on narrower regions along each side of the magnetic inversion line, the magnetic arcade can be easily destabilized by the resistive tearing mode. However, in this case, even though reconnection driven by the tearing mode produces plasmoids, the plasmoid elevation is almost in proportion to the total amount of magnetic helicity contained in the arcade, and it is too slow to explain the trigger process of coronal mass ejections (CMEs). On the other hand, in the case where the shearing motion is imposed on the entire region, much larger magnetic helicity injection is required to injected arcade in order to destabilize the system, compared to practical helicity injection measured in the solar corona. The results suggest that it may be difficult to trigger a CME just by the axisymmetric shearing motion and that some other mechanisms should be involved in the triggering process of a CME. The results also imply that the relation between the magnetic helicity and the overlying magnetic flux can be a key parameter for the CME occurrence. Copyright 2008 by the American Geophysical Union.

    DOI: 10.1029/2007JA012516

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    Scopus

  103. Nonlinear force-free field modeling of a solar active region around the time of a major flare and coronal mass ejection Reviewed

    Schrijver CJ, DeRosa ML, Metcalf T, Barnes G, Lites B, Tarbell T, McTiernan J, Valori G, Wiegelmann T, Wheatland MS, Amari T, Aulanier G, Demoulin P, Fuhrmann M, Kusano K, Regnier S, Thalmann JK

    The Astrophysical Journal   Vol. 675 ( 2 ) page: 1637-1644   2008.3

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    Solar flares and coronal mass ejections are associated with rapid changes in field connectivity and are powered by the partial dissipation of electrical currents in the solar atmosphere. A critical unanswered question is whether the currents involved are induced by the motion of preexisting atmospheric magnetic flux subject to surface plasma flows or whether these currents are associated with the emergence of flux from within the solar convective zone. We address this problem by applying state-of-the-art nonlinear force-free field (NLFFF) modeling to the highest resolution and quality vector-magnetographic data observed by the recently launched Hinode satellite on NOAA AR 10930 around the time of a powerful X3.4 flare. We compute 14 NLFFF models with four different codes and a variety of boundary conditions. We find that the model fields differ markedly in geometry, energy content, and force-freeness. We discuss the relative merits of these models in a general critique of present abilities to model the coronal magnetic field based on surface vector field measurements. For our application in particular, we find a fair agreement of the best-fit model field with the observed coronal configuration, and argue (1) that strong electrical currents emerge together with magnetic flux preceding the flare, (2) that these currents are carried in an ensemble of thin strands, ( 3) that the global pattern of these currents and of field lines are compatible with a large-scale twisted flux rope topology, and (4) that the similar to 10(32) erg change in energy associated with the coronal electrical currents suffices to power the flare and its associated coronal mass ejection.

  104. A quantitative MHD study of the relation among arcade shearing, flux rope formation, and eruption due to the tearing instability Reviewed

    Shiota D, Kusano K, Miyoshi T, Nishikawa N, Shibata K

    JOURNAL OF GEOPHYSICAL RESEARCH-SPACE PHYSICS   Vol. 113 ( A3 ) page: A03S05   2008.3

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    Language:English   Publishing type:Research paper (scientific journal)  

    The quantitative relationship between the magnetohydrodynamic ( MHD) activity of solar coronal arcade and the magnetic helicity injection, which is caused by shearing motion, has been investigated, using azimuthally symmetric model of MHD simulation. We have calculated several cases in which the width of the shearing region is varied and examined the relationship between the magnetic arcade dynamics and magnetic helicity evolution. As a result, it is found that as the shearing motion is imposed on narrower regions along each side of the magnetic inversion line, the magnetic arcade can be easily destabilized by the resistive tearing mode. However, in this case, even though reconnection driven by the tearing mode produces plasmoids, the plasmoid elevation is almost in proportion to the total amount of magnetic helicity contained in the arcade, and it is too slow to explain the trigger process of coronal mass ejections ( CMEs). On the other hand, in the case where the shearing motion is imposed on the entire region, much larger magnetic helicity injection is required to injected arcade in order to destabilize the system, compared to practical helicity injection measured in the solar corona. The results suggest that it may be difficult to trigger a CME just by the axisymmetric shearing motion and that some other mechanisms should be involved in the triggering process of a CME. The results also imply that the relation between the magnetic helicity and the overlying magnetic flux can be a key parameter for the CME occurrence.

  105. Nonlinear force-free field modeling of a solar active region around the time of a major flare and coronal mass ejection Reviewed

    C. J. Schrijver, M. L. DeRosa, T. Metcalf, G. Barnes, B. Lites, T. Tarbell, J. McTiernan, G. Valori, T. Wiegelmann, M. S. Wheatland, T. Amari, G. Aulanier, P. Demoulin, M. Fuhrmann, K. Kusano, S. Regnier, J. K. Thalmann

    ASTROPHYSICAL JOURNAL   Vol. 675 ( 2 ) page: 1637 - 1644   2008.3

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    Language:English   Publishing type:Research paper (scientific journal)   Publisher:IOP PUBLISHING LTD  

    Solar flares and coronal mass ejections are associated with rapid changes in field connectivity and are powered by the partial dissipation of electrical currents in the solar atmosphere. A critical unanswered question is whether the currents involved are induced by the motion of preexisting atmospheric magnetic flux subject to surface plasma flows or whether these currents are associated with the emergence of flux from within the solar convective zone. We address this problem by applying state-of-the-art nonlinear force-free field (NLFFF) modeling to the highest resolution and quality vector-magnetographic data observed by the recently launched Hinode satellite on NOAA AR 10930 around the time of a powerful X3.4 flare. We compute 14 NLFFF models with four different codes and a variety of boundary conditions. We find that the model fields differ markedly in geometry, energy content, and force-freeness. We discuss the relative merits of these models in a general critique of present abilities to model the coronal magnetic field based on surface vector field measurements. For our application in particular, we find a fair agreement of the best-fit model field with the observed coronal configuration, and argue (1) that strong electrical currents emerge together with magnetic flux preceding the flare, (2) that these currents are carried in an ensemble of thin strands, ( 3) that the global pattern of these currents and of field lines are compatible with a large-scale twisted flux rope topology, and (4) that the similar to 10(32) erg change in energy associated with the coronal electrical currents suffices to power the flare and its associated coronal mass ejection.

    DOI: 10.1086/527413

    Web of Science

  106. Multi-physics plasma simulation by the interlocking of two different hybrid models Reviewed

    T. Sugiyama, K. Kusano

    NUMERICAL MODELING OF SPACE PLASMA FLOWS: ASTRONUM-2007   Vol. 385   page: 228 - 233   2008

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    Language:English   Publishing type:Research paper (international conference proceedings)   Publisher:ASTRONOMICAL SOC PACIFIC  

    We have developed a new interlocked simulation model to connect an Ion-Particle Hybrid simulation model (Hybrid) and an Energetic-Particle Hybrid simulation (EP-Hyb) model. In the conventional Ion-Particle Hybrid model, all ions are kinetically treated as particles. In the EP-Hyb model, non-thermal energetic ions are kinetically treated, and the thermal component is calculated as a fluid. The interlocked model is applied to an one-dimensional collision-less shock problem. The data of each hybrid model are exchanged through the boundary at every time-step. Resultantly, the present simulation can handle the full ion kinetics to investigate the injection problem at the shock transition region by the Hybrid model, and also the wave-particle interactions even in the far upstream region to investigate the diffusive acceleration process by the EP-Hyb model. Since the calculation cost of the EP-Hyb model is much smaller than that of the Hybrid model, with the interlocked simulation we can considerably reduce the computational demand.

    Web of Science

  107. Three-Dimensional Structure Analysis of Coronal Magnetic Field in AR NOAA 10930 Based on Vector Magnetogram Observations with Hinode/SOT Reviewed

    S. Inoue, K. Kusano, S. Masuda, T. Miyoshi, T. Yamamoto, T. Magara, T. Tsuneta, T. Sakurai, T. Yokoyama

    FIRST RESULTS FROM HINODE   Vol. 397   page: 110 - +   2008

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    Language:English   Publishing type:Research paper (international conference proceedings)   Publisher:ASTRONOMICAL SOC PACIFIC  

    Active region NOAA 10930 produced the first X-class flare observed by the Hinode satellite. Fortunately, the data covers the time span before and after the X-class flare arising on December 13, 2006 in this active region. During this event, the Hinode satellite clearly observed the typical features of a flare: two ribbon and post flare loop structures seen by SOT, sigmoidal structure before the onset, and subsequent cusp loop structure seen by XRT. We analyzed the three-dimensional magnetic structure of the region before and after the flare on Dec.13, 2006 using the Non-Linear Force-Free (NLFF) extrapolation method based on extended magnetofrictional method.
    As a result of the NLFF extrapolation, we found that, before the flare onset, strong sheared structures were formed on the neutral line. Furthermore, we revealed that a sigmoidal structure was not formed of a single loop, but was composed of strong multiple sheared field. On other the hand, after the flare, elongated magnetic flux is partially formed and a part of magnetic shear was released. The result indicates that the part; of NLFF relaxes toward the potential like field in this event.

    Web of Science

  108. Robust and efficient Riemann solvers for MHD Reviewed

    T. Miyoshi, K. Kusano

    NUMERICAL MODELING OF SPACE PLASMA FLOWS: ASTRONUM-2007   Vol. 385   page: 279 - +   2008

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    Language:English   Publishing type:Research paper (international conference proceedings)   Publisher:ASTRONOMICAL SOC PACIFIC  

    Robust and efficient approximate Riemann solvers for magnetohydrodynamics (MHD) are constructed. Particularly, a family of positively conservative Harten-Lax-van Leer (HLL)-type Riemann solvers, the so-called HLLD ('D' denotes Discontinuities), HLLR ('R' denotes Rotational), HLLC ('C' denotes Contact), and HLL solvers, is systematically considered.

    Web of Science

  109. Three-Dimensional Structure Analysis of Coronal Magnetic Field in AR NOAA 10930 Based on Vector Magnetogram Observations with Hinode/SOT

    Inoue S., Kusano K., Masuda S., Miyoshi T., Yamamoto T., Magara T., Tsuneta T., Sakurai T., Yokoyama T.

    FIRST RESULTS FROM HINODE   Vol. 397   page: 110 - +   2008

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    Web of Science

  110. Tests and comparisons of velocity-inversion techniques Reviewed

    Welsch BT, Abbett WP, DeRosa ML, Fisher GH, Georgoulis MK, Kusano K, Longcope DW, Ravindra B, Schuck PW

    The Astrophysical Journal   Vol. 670 ( 2 ) page: 1434-1452   2007.12

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    Recently, several methods that measure the velocity of magnetized plasma from time series of photospheric vector magnetograms have been developed. Velocity fields derived using such techniques can be used both to determine the fluxes of magnetic energy and helicity into the corona, which have important consequences for understanding solar flares, coronal mass ejections, and the solar dynamo, and to drive time-dependent numerical models of coronal magnetic fields. To date, these methods have not been rigorously tested against realistic, simulated data sets, in which the magnetic field evolution and velocities are known. Here we present the results of such tests using several velocity-inversion techniques applied to synthetic magnetogram data sets, generated from anelastic MHD simulations of the upper convection zone with the ANMHD code, in which the velocity field is fully known. Broadly speaking, the MEF, DAVE, FLCT, IM, and ILCT algorithms performed comparably in many categories. While DAVE estimated the magnitude and direction of velocities slightly more accurately than the other methods, MEF's estimates of the fluxes of magnetic energy and helicity were far more accurate than any other method's. Overall, therefore, the MEF algorithm performed best in tests using the ANMHD data set. We note that ANMHD data simulate fully relaxed convection in a high-beta plasma, and therefore do not realistically model photospheric evolution.

  111. Multi-scale plasma simulation by the interlocking of magnetohydrodynamic model and particle-in-cell kinetic model Reviewed

    Sugiyama T, Kusano K

    JOURNAL OF COMPUTATIONAL PHYSICS   Vol. 227 ( 2 ) page: 1340-1352   2007.12

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    Many kinds of simulation models have been developed to understand the complex plasma systems. However, these simulation models have been separately performed because the fundamental assumption of each model is different and restricts the physical processes in each spatial and temporal scales. On the other hand, it is well known that the interactions among the multiple scales may play crucial roles in the plasma phenomena (e.g. magnetic reconnection. collisionless shock), where the kinetic processes in the micro-scale may interact with the global structure in the fluid dynamics. To take self-consistently into account such multi-scale phenomena, we have developed a new simulation model by directly interlocking the fluid simulation of the magnetohyrdodynamics (MHD) model and the kinetic simulation of the particle-in-cell (PIC) model. The PIC domain is embedded in a small part of MHD domain. The both simulations are performed simultaneously in each domain and the bounded data are frequently exchanged each other to keep the consistency between the models. We have applied our new interlocked simulation to Alfven wave propagation problem as a benchmark test and confirmed that the waves can propagate smoothly through the boundaries of each domain. (C) 2007 Elsevier Inc. All rights reserved.

  112. Multi-scale plasma simulation by the interlocking of magnetohydrodynamic model and particle-in-cell kinetic model Reviewed

    Tooru Sugiyama, Kanya Kusano

    JOURNAL OF COMPUTATIONAL PHYSICS   Vol. 227 ( 2 ) page: 1340 - 1352   2007.12

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    Language:English   Publishing type:Research paper (scientific journal)   Publisher:ACADEMIC PRESS INC ELSEVIER SCIENCE  

    Many kinds of simulation models have been developed to understand the complex plasma systems. However, these simulation models have been separately performed because the fundamental assumption of each model is different and restricts the physical processes in each spatial and temporal scales. On the other hand, it is well known that the interactions among the multiple scales may play crucial roles in the plasma phenomena (e.g. magnetic reconnection. collisionless shock), where the kinetic processes in the micro-scale may interact with the global structure in the fluid dynamics. To take self-consistently into account such multi-scale phenomena, we have developed a new simulation model by directly interlocking the fluid simulation of the magnetohyrdodynamics (MHD) model and the kinetic simulation of the particle-in-cell (PIC) model. The PIC domain is embedded in a small part of MHD domain. The both simulations are performed simultaneously in each domain and the bounded data are frequently exchanged each other to keep the consistency between the models. We have applied our new interlocked simulation to Alfven wave propagation problem as a benchmark test and confirmed that the waves can propagate smoothly through the boundaries of each domain. (C) 2007 Elsevier Inc. All rights reserved.

    DOI: 10.1016/j.jcp.2007.09.011

    Web of Science

  113. Tests and comparisons of velocity-inversion techniques Reviewed

    B. T. Welsch, W. P. Abbett, M. L. DeRosa, G. H. Fisher, M. K. Georgoulis, K. Kusano, D. W. Longcope, B. Ravindra, P. W. Schuck

    ASTROPHYSICAL JOURNAL   Vol. 670 ( 2 ) page: 1434 - 1452   2007.12

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    Language:English   Publishing type:Research paper (scientific journal)   Publisher:IOP PUBLISHING LTD  

    Recently, several methods that measure the velocity of magnetized plasma from time series of photospheric vector magnetograms have been developed. Velocity fields derived using such techniques can be used both to determine the fluxes of magnetic energy and helicity into the corona, which have important consequences for understanding solar flares, coronal mass ejections, and the solar dynamo, and to drive time-dependent numerical models of coronal magnetic fields. To date, these methods have not been rigorously tested against realistic, simulated data sets, in which the magnetic field evolution and velocities are known. Here we present the results of such tests using several velocity-inversion techniques applied to synthetic magnetogram data sets, generated from anelastic MHD simulations of the upper convection zone with the ANMHD code, in which the velocity field is fully known. Broadly speaking, the MEF, DAVE, FLCT, IM, and ILCT algorithms performed comparably in many categories. While DAVE estimated the magnitude and direction of velocities slightly more accurately than the other methods, MEF's estimates of the fluxes of magnetic energy and helicity were far more accurate than any other method's. Overall, therefore, the MEF algorithm performed best in tests using the ANMHD data set. We note that ANMHD data simulate fully relaxed convection in a high-beta plasma, and therefore do not realistically model photospheric evolution.

    DOI: 10.1086/522422

    Web of Science

  114. Helicity injection in regions of various magnetic fluxes Reviewed

    Tetsuya T. Yamamoto, Takashi Sakurai, Kanya Kusano, Takaaki Yokoyama

    NEW SOLAR PHYSICS WITH SOLAR-B MISSION   Vol. 369   page: 179 - +   2007

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    Language:English   Publishing type:Research paper (international conference proceedings)   Publisher:ASTRONOMICAL SOC PACIFIC  

    In this study, we investigated magnetic helicity injection rates among active regions of various sizes. We analyzed 78 active regions (more than 600 magnetograms), using the vector magnetograms obtained with the Solar Flare Telescope of NAOJ and SoHO/MDI magnetograms. We used a method proposed by Kusano et al. (2002, 2004) to evaluate the helicity injection. Magnetic fluxes of analyzed regions are from 2 x 10(12) Wb to 4 x 10(14) Wb. Unsigned magnetic helicity injection rates are from 10(19) Wb(2) s(-1) to 10(23) Wb(2) S-1. From a scatter plot of the magnetic flux and the unsigned magnetic helicity injection rate, we found that the magnetic helicity injection rate has an upper limit for a given value of the magnetic flux, and this upper limit is inversely proportional to the magnetic flux. We discuss these results with a model of the helicity injection due to helical turbulence (E-Effect, Longcope, Fisher, & Pevtsov 1998).

    Web of Science

  115. Three-dimensional filament eruption driven by an emerging flux Reviewed

    Shun Notoya, Takaaki Yokoyama, Kanya Kusano, Takashi Sakurai, Takehiro Miyagoshi, Hiroaki Isobe, Tetsuya Yamamoto

    NEW SOLAR PHYSICS WITH SOLAR-B MISSION   Vol. 369   page: 381 - +   2007

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    Language:English   Publishing type:Research paper (international conference proceedings)   Publisher:ASTRONOMICAL SOC PACIFIC  

    Some important observations have shown that the strong correlation between emerging flux and eruptions of quiescent filaments (Feynman & Martin, 1995; Wang & Sheeley, 1999). Chen & Shibata (2000) performed two-dimensional simulations including a flux rope in the corona, and their results suggest that the eruption process is triggered by the emerging flux through the reconnection. Our purpose in this paper is to investigate that '' how a filament is produced and how an eruption process can be initiated by the emerging flux and what effects of three-dimensionality appear in the process of eruption ''. For that purpose, we performed three-dimensional numerical simulations of the emerging flux model. nom our results, a filamentary structure is produced from the coronal arcade field by the reconnection process, and when the reconnection process proceeds effectively, the produced structure is ejected by the magnetic force. These processes can thought to be a new mechanism of the eruption which is different from, for example, the one in Fan & Gibson (2004).

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  116. The japan multi-institutional collaborative cohort study (JMICC study) to detect gene-environment interactions for cancer

    Hamajima Nobuyuki, Wakai Kenji, Naito Mariko, Nishio Kazuko, Ishida Yoshiko, Okada Rieko, Masui Kaori, Morita Emi, Kuroishi Tetsuo, Mikami Haruo, Ohira Miki, Fujimoto Shuichi, Takayama Kimiko, Asai Yatami, Suzuki Masurni, Fukada Hiroko, Tomoda Akiko, Misu Yasoko, Katase Shiro, Tokumasu Satoru, Kato Yoko, Yoichi Murakami, Atsushi Koyama, Tajima Kazuo, Hirose Kaoru, Hiraki Akio, Matsuo Keitaro, Suzuki Takeshi, Kuriki Kiyonori, Saito Toshiko, Watanabe Miki, Suzuki Sadao, Tokudome Shinkan, Hosono Akihiro, Arakawa Kazuyuki, Hattori Nami, Ando Ryosuke, Tanaka Tsutomu, Kitabayashi Yukiko, Ueshima Hirotsugu, Kita Yoshikuni, Nakamura Yasuyuki, Matsui Kenji, Yamamoto Takako, Chowdhury Turin Tanvir, Sugihara Hideki, Morita Yutaka, Tomioka Nobuyoshi, Watanabe Yoshiyuki, Ozasa Kotarc, Yuge Mariko, Hayashi Kyohei, Shigeta Masako, Mitani Satoko, Ozaki Etsuko, Matsui Daisuke, sakazaki Tomio, Uemura Hirokazu, Hiyoshi Mineyoshi, Sagara Yasunobu, Kono Suminori, Yin Guang, Nagano Jun, Mizoue Tetsuya, Takayanagi Ryoichi, Ohnaka Keizo, Kawate Hisaya, Adachi Masahiro, Moore Malcolm A., Toyomura Kengo, Isomura Kayoko, Hagiwara Tomoko, Fukumoto Jin, Nanri Akiko, Yamaji Taiki, Yoshida Daigo, Morita Makiko, Ueda Naoyuki, Maki Takako, Ikeda Mizuko, Tanaka Keitaro, Shinchi Koichi, Higaki Yasuki, Hara Megumi, Sakamoto Tatsuhiko, Imaizumi Takeshi, Taguchi Naoto, Horita Mikako, Takezaki Toshiro, Niimura Hideshi, Hirasada Kazuyo, Tatebou Masaya, Noriko Tsunematsu, Kusano Ken, Maruyama Eiji, Orii Yuka, Sato Keiko, Masui Toru, Tamakoshi Akiko, Hashimoto Shuji, Nakachi Kei, Imai Kazue, Eguchi Hidetaka, Takahashi Takashi, Okayama Akira, Kurosawa Yoichi, Nakayama Takeo, Muto Kaori, Yamagata Zentaro

    ASIAN PACIFIC JOURNAL OF CANCER PREVENTION   Vol. 8 ( 2 ) page: 317-323   2007

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  117. Simulation study of transition process from long-lived sigmoid to flare eruption Reviewed

    Kanya Kusano

    NEW SOLAR PHYSICS WITH SOLAR-B MISSION   Vol. 369   page: 469 - 475   2007

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    The formation mechanism of sigmoidal structure in the solar corona and the transition process from long-lived sigmoid to flare eruption are studied on the basis of the Taylor's minimum energy principle and the three-dimensional magnetohydrodynamic numerical simulations. The simulation results indicate that magnetic reconnection driven by the resistive tearing mode instability growing on current sheet, where magnetic shear is steeply reversed, may cause the formation of sigmoidal structure. The mechanism of that can be explained as the spontaneous manifestation of the Taylor's minimum energy state in magnetic arcade geometry. Furthermore, it is also numerically demonstrated that the formation of sigmoid can be followed by the eruption of magnetic flux. In the eruption, however, the sigmoidal flux itself is not ejected upward, but it is collapsed by the reconnection with overlaying magnetic field. The results are consistent with the reversed shear flare model recently proposed by Kusano et al., which predicts that the coronal eruption is triggered by the collapsing of magnetic arcade due to the annihilation of positive and negative magnetic helicity.

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  118. Simulation study of three-dimensional and nonlinear dynamics of flux tube in the solar corona Reviewed

    Satoshi Inoue, Kanya Kusano

    NEW SOLAR PHYSICS WITH SOLAR-B MISSION   Vol. 369   page: 421 - +   2007

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    We numerically investigated the three-dimensional (3D) stability and the nonlinear dynamics of flux tube embedded in magnetic arcade. As a results, we found that the flux tube is unstable to the kink mode instability, as the system approach to the loss-of-equilibrium state. The 3D simulation shows that when the flux tube is long enough, it can escape from arcade with almost constant speed after the accelerated launching due to the kink instability. In the case of the short flux tube, however, the flux tube ascending is failed at some height. The strong current sheet is formed in the lower part of the long flux tube at late phase as a consequence of the instability, whereas the current sheet can not be maintained in the case of short flux tube. Therefore, the formation of the current sheet at late phase may have some relation to the ejective eruption of the flux tube.

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  119. Macro-micro interlocked simulation for multiscale phenomena Reviewed

    Kanya Kusano, Shigenobu Hirose, Torn Sugiyama, Shinichiro Shima, Akio Kawano, Hiroki Hasegawa

    COMPUTATIONAL SCIENCE - ICCS 2007, PT 1, PROCEEDINGS   Vol. 4487   page: 914 - +   2007

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    A new methodology for the, simulation of multiscale processes, called Macro-Micro Interlocked (MMI) Simulation, is introduced. The MMI simulation is carried out by the two-way connection of different numerical models, which may handle macroscopic and microscopic dynamics, respectively. The MMI simulation are applied to several multiscale phenomena, for instance, cloud formation, gas detonation, and plasma dynamics. The results indicate that the MMI simulation provide us an effective and prospective framework for multiscale simulation.

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  120. Macro-micro economic system simulation Reviewed

    B. S S Onggo, K. Kusano, T. Sato

    Proceedings - Workshop on Principles of Advanced and Distributed Simulation, PADS     page: 105 - 112   2007

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    The compute power required in the simulation of mutually cooperating systems in the physical sciences is huge. Therefore, it is common to simulate one system and treat others as parameters or environmental conditions to the simulated system. Macro-Micro Interlocked (MMI) simulation framework has been proposed to simulate such cooperating systems. In this paper, we study the feasibility of applying this framework on the simulation of macro-micro economic model. This simulation allows us to observe the system's behaviour at the macro and micro levels concurrently. Policy changes at the macroeconomic level may affect the behaviour of the entities at the microeconomic level. Similarly, the behaviour changes at the microeconomic level may effect the macroeconomic system. We implement an MMI simulation library suitable for execution on a cluster of PCs. At this early stage, the experiment shows a promising result which provides us with a foundation to experiment with a larger model. © 2007 IEEE.

    DOI: 10.1109/PADS.2007.22

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  121. Simulation study of the Solar flare onset mechanism and the self-organization in the Solar coronal plasma Reviewed

    Kusano K, Nishikawa N, Inoue S, Maeshiro T, Sakurai T

    JOURNAL OF PLASMA PHYSICS   Vol. 72 ( 6 ) page: 979-982   2006.12

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    Three-dimensional magnetohydrodynamics of the Solar coronal plasma is investigated by numerical simulation, aiming to understand the mechanisms of the Solar flare onset. It is demonstrated by the simulations that the resistive tearing mode instability growing on the magnetic shear inversion layer can drive the large-scale eruption through the mutual excitation of double reconnections. It is also revealed that the instability is able to cause the magnetohydrodynamic energy relaxation, in which the typical sigmoidal structure is self-organized prior to the onset of eruption. The Simulation results predict that both the formation of sigmoids and the onset of flares should occur around the electric current sheet where the magnetic shear is steeply reversed. It is consistent with the reversed-shear flare model and the vector magnetograph observations.

  122. MHD-PIC connection model in a magnetosphere-ionosphere coupling system Reviewed

    T. Sugiyama, K. Kusano, S. Hirose, A. Kageyama

    JOURNAL OF PLASMA PHYSICS   Vol. 72   page: 945 - 948   2006.12

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    A new simulation model is developed, in which the interaction between the macroscopic and microscopic plasma processes is able to be taken into account self-consistently. Magnetohydrodynamic (MHD) simulation and particle-in-cell (PIC) simulation are directly connected and performed simultaneously. This MHD-PIC connection model is first applied to the study of the quiet auroral are formation process. It is an example of our challenge to create the holistic simulation framework, that is, the heterogeneous schemes that can be unified by the state-of-the-art numerical technique. In this paper, we will explain the algorithm of our new model and show the results which have been calculated on the Earth Simulator.

    DOI: 10.1017/S0022377806005356

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  123. Virtual reality visualization by CAVE with VFIVE and VTK Reviewed

    N. Ohno, A. Kageyama, K. Kusano

    JOURNAL OF PLASMA PHYSICS   Vol. 72   page: 1069 - 1072   2006.12

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    The CAVE-type virtual reality (VR) system was introduced for scientific visualization of large-scale data in the plasma simulation community about a decade ago. Since then, we have been developing a VR visualization software. VFIVE, for general CAVE systems. Recently, we have integrated an open-source visualization library, the Visualization Toolkit (VTK), into VFIVE. Various visualization methods of TTK can be incorporated and used interactively in VFIVE.

    DOI: 10.1017/S0022377806005253

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  124. Simulation study of the Solar flare onset mechanism and the self-organization in the Solar coronal plasma Reviewed

    K. Kusano, N. Nishikawa, S. Inoue, T. Maeshiro, T. Sakurai

    JOURNAL OF PLASMA PHYSICS   Vol. 72   page: 979 - 982   2006.12

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    Language:English   Publishing type:Research paper (scientific journal)   Publisher:CAMBRIDGE UNIV PRESS  

    Three-dimensional magnetohydrodynamics of the Solar coronal plasma is investigated by numerical simulation, aiming to understand the mechanisms of the Solar flare onset. It is demonstrated by the simulations that the resistive tearing mode instability growing on the magnetic shear inversion layer can drive the large-scale eruption through the mutual excitation of double reconnections. It is also revealed that the instability is able to cause the magnetohydrodynamic energy relaxation, in which the typical sigmoidal structure is self-organized prior to the onset of eruption. The Simulation results predict that both the formation of sigmoids and the onset of flares should occur around the electric current sheet where the magnetic shear is steeply reversed. It is consistent with the reversed-shear flare model and the vector magnetograph observations.

    DOI: 10.1017/S0022377806005423

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  125. Three-dimensional simulation study of flux rope dynamics in the solar corona Reviewed

    S. Inoue, K. Kusano

    ASTROPHYSICAL JOURNAL   Vol. 645 ( 1 ) page: 742 - 756   2006.7

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    The three-dimensional stability and the nonlinear dynamics of a flux rope embedded in a magnetic arcade are investigated using magnetohydrodynamic (MHD) simulations, with the goal of understanding the mechanism of filament eruption in the solar corona. The flux rope equilibrium proposed by Forbes in 1990 is adopted as the initial state of the three-dimensional simulation, and we find that the equilibrium is linearly unstable to the kink mode instability, when the system approaches the loss-of-equilibrium state. The three-dimensional simulation demonstrates that when the flux rope is long enough, it can escape from the arcade at an almost constant speed after the accelerated launching phase due to the kink instability. The continuous ascending of the flux rope is driven by the nonlinear growth of several kink modes. In the case of a short flux rope, however, the flux rope ascension fails at some height. This suggests that the flux rope eruption must proceed through the multiple stages, which are driven by the loss of stability in the launching phase and by the loss of equilibrium in the late ascending phase. Since the short rope could not come up to the critical height for the transition from the first to the second stage, the ascending must stop. The role of magnetic reconnection in the late ascending phase and the formation mechanism of density cavity, which corresponds to dimming region observed in CMEs, is also discussed using the simulation results.

    DOI: 10.1086/503153

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  126. Nonlinear effects on magnetic energy release by forced magnetic reconnection: Long wavelength perturbations Reviewed

    Rekha Jain, Philippa Browning, K. Kusano

    PHYSICS OF PLASMAS   Vol. 13 ( 5 )   2006.5

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    Two-dimensional, nonlinear magnetohydrodynamic simulations in a compressible plasma to investigate magnetic energy release during the process of forced magnetic reconnection are carried out. This is in order to study the heating of the Sun's corona where it is believed that reconnection is induced by the photospheric motions. A sheared force-free field is perturbed by a transitory slow disturbance (pulse) at the boundary. This disturbance triggers the formation of a current sheet that subsequently releases stored magnetic energy through magnetic reconnection. Previously, it has been shown that for small boundary perturbations, the simulation results are consistent with the previous analytic theory based on a linear approach. For larger amplitude perturbations, or close to the threshold for tearing instability, the evolution shows nonlinear behavior. Solar coronal heating may arise due to a series of reconnection events, and a primary aim of this work is to study the interaction of such heating events. Thus, the perturbations are applied at the boundary by successive pulses. It is found that following the second driving pulse, the current sheet expands along the separatrix before relaxing to a reconnective equilibrium with magnetic islands and releasing even more magnetic energy for the same amplitude perturbation. Here, the previous work is extended to study long wavelength perturbations for which the system exhibits even stronger nonlinear aspects. (c) 2006 American Institute of Physics.

    DOI: 10.1063/1.2200630

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  127. Simulation study of the formation mechanism of sigmoidal structure in the solar corona Reviewed

    K Kusano

    ASTROPHYSICAL JOURNAL   Vol. 631 ( 2 ) page: 1260 - 1269   2005.10

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    The formation mechanism of sigmoidal structure in the solar coronal magnetic field is studied using the three-dimensional magnetohydrodynamic numerical simulations, based on the so-called reversed-shear flare model recently proposed by Kusano et al. The simulation results clearly indicate that magnetic reconnection driven by the resistive tearing mode instability growing on the magnetic shear inversion layer can cause the spontaneous formation of sigmoidal structure. Furthermore, it is also numerically demonstrated that the formation of the sigmoids can be followed by the explosive energy liberation, if the sigmoids contain sufficient magnetic flux. This implies that the reversed-shear flare model can provide a self-consistent explanation for the formation of sigmoids as well as for the onset of eruption, which is driven by magnetic reconnection above sigmoids. The geometric relationship between the sigmoidal structure and the minimum energy state predicted by J. B. Taylor in 1974 is examined. The result suggests that the sigmoidal formation could be understood as a manifestation of the minimum energy state, which has the excess magnetic helicity compared to the bifurcation criterion of the linear force-free field. The consistency with the observations of magnetic helicity is also discussed.

    DOI: 10.1086/432570

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  128. A multi-state HLL approximate Riemann solver for ideal magnetohydrodynamics Reviewed

    Takahiro Miyoshi, Kanya Kusano

    Journal of Computational Physics   Vol. 208 ( 1 ) page: 315 - 344   2005.9

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    Language:English   Publishing type:Research paper (scientific journal)   Publisher:ACADEMIC PRESS INC ELSEVIER SCIENCE  

    A new multi-state Harten-Lax-van Leer (HLL) approximate Riemann solver for the ideal magnetohydrodynamic (MHD) equations is developed based on the assumption that the normal velocity is constant over the Riemann fan. This assumption is same as that used in the HLLC ("C" denotes Contact) approximate Riemann solver for the Euler equations. From the assumption, it is naturally derived that the Riemann fan should consist of four intermediate states for Bx ≠ 0, whereas the number of the intermediate states is reduced to two when Bx = 0. Since the intermediate states satisfied with all jump conditions in this approximate Riemann system are analytically obtained, the multi-state HLL Riemann solver can be constructed straightforwardly. It is shown that this solver can exactly resolve isolated discontinuities formed in the MHD system, and hence named as HLLD Riemann solver. (Here, "D" stands for Discontinuities.) It is also analytically proved that the HLLD Riemann solver is positively conservative like the HLLC Riemann solver. Indeed, the HLLD Riemann solver corresponds to the HLLC Riemann solver when the magnetic field vanishes. Numerical tests demonstrate that the HLLD Riemann solver is more robust and efficient than the linearized Riemann solver, and its resolution is equally good. It indicates that the HLLD solver must be useful in practical applications for the ideal MHD equations. © 2005 Elsevier Inc. All rights reserved.

    DOI: 10.1016/j.jcp.2005.02.017

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  129. *Simulation Study of the Formation Mechanism of Sigmoidal Structure in the Solar Corona Invited Reviewed

    Kusano, K.

    The Astrophysical Journal   Vol. 631 ( 2 ) page: 1260-1269   2005.5

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    The formation mechanism of sigmoidal structure in the solar coronal magnetic field is studied using the three-dimensional magnetohydrodynamic numerical simulations, based on the so-called reversed-shear flare model recently proposed by Kusano et al. The simulation results clearly indicate that magnetic reconnection driven by the resistive tearing mode instability growing on the magnetic shear inversion layer can cause the spontaneous formation of sigmoidal structure. Furthermore, it is also numerically demonstrated that the formation of the sigmoids can be followed by the explosive energy liberation, if the sigmoids contain sufficient magnetic flux. This implies that the reversed-shear flare model can provide a self-consistent explanation for the formation of sigmoids as well as for the onset of eruption, which is driven by magnetic reconnection above sigmoids. The geometric relationship between the sigmoidal structure and the minimum energy state predicted by J. B. Taylor in 1974 is examined. The result suggests that the sigmoidal formation could be understood as a manifestation of the minimum energy state, which has the excess magnetic helicity compared to the bifurcation criterion of the linear force-free field. The consistency with the observations of magnetic helicity is also discussed.

  130. Magnetic helicity injection and sigmoidal coronal loops Reviewed

    TT Yamamoto, K Kusano, T Maeshiro, T Yokoyama, T Sakurai

    ASTROPHYSICAL JOURNAL   Vol. 624 ( 2 ) page: 1072 - 1079   2005.5

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    We studied the relationship between magnetic helicity injection and the formation of sigmoidal loops. We analyzed seven active regions: three regions showed coronal loops similar to the potential field, and four regions showed the sigmoidal loops. The magnetic helicity injection rate was evaluated using the method proposed by Kusano et al. In order to compare the helicity of regions of various sizes, we defined the normalized helicity injection rate as the magnetic helicity injection rate divided by the magnetic flux squared. We found that the sigmoidal regions and nonsigmoidal regions have comparable normalized helicity injection rates. Next, we calculated the magnetic helicity content of the sigmoidal loops by using the magnetic flux tube model (Longcope & Welsch) and compared it with the magnetic helicity injected from around the footpoints of three sigmoidal loops. For two sigmoidal loops, it is found that these values are comparable. Another loop showed significant disagreement between helicity injection rate and its magnetic helicity content. Excluding this region on the basis of its complexity ( perhaps multiple loops forming a sigmoidal loop), we can conclude that geometric twist of the sigmoidal loops is consistent with the magnetic helicity injected from around the footpoints of the sigmoidal loops.

    DOI: 10.1086/429363

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  131. A statistical study of the correlation between magnetic helicity injection and soft X-ray activity in solar active regions Reviewed

    T Maeshiro, K Kusano, T Yokoyama, T Sakurai

    ASTROPHYSICAL JOURNAL   Vol. 620 ( 2 ) page: 1069 - 1084   2005.2

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    The correlation between magnetic helicity injection across the photosphere and soft X-ray activity in the solar corona is statistically investigated for seven active regions appearing in the years 1997 - 2000. The magnetic helicity flux into the solar corona is analyzed by the induction equation method, using magnetograms observed by the Michelson Doppler Imager on SOHO and by the vector magnetograph at the National Astronomical Observatory of Japan. Soft X-ray activity is evaluated from the data observed by the Yohkoh soft X-ray telescope (SXT). Soft X-ray activity of active regions in nonflare phases is found to correlate better with unsigned magnetic helicity flux than with the simple integration of the magnetic helicity flow. In addition, several magnetic variables, e. g., magnetic flux and electric current flux, are investigated, and it is confirmed that any fluxes given by the area integration of magnetic variables are well correlated with soft X-ray activity. However, for themagnetic helicity flow, not only the whole area flux but also the local intensity correlates well with the soft X-ray intensity. The relation between the spatial structure of the magnetic shear and soft X-ray activity is also investigated, and it is revealed that structural complexity in the magnetic shear tends to increase the efficiency of energy liberation in the solar corona. These results indicate that the magnetic helicity injected from the photosphere is relevant to the heating process in the solar corona, although several magnetic variables, not only magnetic helicity, could be related to that.

    DOI: 10.1086/426806

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  132. Solar coronal heating by forced magnetic reconnection: Multiple reconnection events Reviewed

    R Jain, P Browning, K Kusano

    PHYSICS OF PLASMAS   Vol. 12 ( 1 )   2005.1

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    Magnetic reconnection is a strong candidate for a coronal heating mechanism, and heating by forced magnetic reconnection is investigated here. Two dimensional, nonlinear magnetohydrodynamic simulations are used to investigate forced magnetic reconnection in a compressible plasma. The reconnection occurs when a sheared force-free field is perturbed by a slow disturbance (pulse) at the boundary which is representative of the solar corona where the reconnection is induced by the photospheric motions. The case of driving by successive pulses, which generate a series of heating events which may interact with each other, is considered. This is in order to model the heating of the corona by a series of nanoflare events. For small perturbations, the simulation results are consistent with the previous analytic theory based on linear approach where a current sheet is formed initially at the resonant surface followed by reconnection and then release of magnetic energy. For large amplitude perturbations, or close to the threshold for tearing instability, the system exhibits strong nonlinear aspects. Following the second driving pulse, the current sheet expands along the separatrix before relaxing to a reconnective equilibrium and releasing even more magnetic energy for the same amplitude perturbation. (C) 2005 American Institute of Physics.

    DOI: 10.1063/1.1831278

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  133. Generation and annihilation of magnetic helicity in active regions Reviewed

    K. Kusano

    HIGHLIGHTS OF ASTRONOMY, VOL 13   Vol. 13   page: 113 - 116   2005

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    Language:English   Publishing type:Research paper (scientific journal)   Publisher:ASTRONOMICAL SOC PACIFIC  

    Generation and annihilation processes of magnetic helicity in solar coronal active regions are investigated based on the observations and the simulations. We first examined the reliability of the numerical techniques, which enable to measure the magnetic helicity flux through the photosphere based on the magnetogram data. Secondly, in terms of the new technique, we found that magnetic helicities of the both signs are simultaneously injected into active regions. Motivated by this result, finally, we investigated the nonlinear process of the magnetic helicity annihilation, using the three-dimensional numerical simulations. The simulations clearly indicated that the helicity reversal can cause the eruption of large-scale plasmoid through the nonlinear process of the resistive instability growing on the helicity inversion layer. From these studies, we point out that the annihilation of magnetic helicity is a key process for the onset mechanism of solar flares.

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  134. Study of the relationship between magnetic helicity and solar coronal activity Reviewed

    K Kusano

    CORONAL AND STELLAR MASS EJECTIONS   ( 226 ) page: 256 - 256   2005

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    Language:English   Publishing type:Research paper (international conference proceedings)   Publisher:CAMBRIDGE UNIV PRESS  

    DOI: 10.1017/S1743921305000669

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  135. *The trigger mechanism of solar flares in a coronal arcade with reversed magnetic shear Reviewed

    Kusano K, Maeshiro T, Yokoyama T, Sakurai T

    The Astrophysical Journal   Vol. 610 ( 1 ) page: 537-549   2004.7

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    We have investigated the possibility that magnetic reconnection between oppositely sheared magnetic loops works as a trigger mechanism of solar flares, based on three-dimensional numerical simulations. The simulations were carried out by applying a slow footpoint motion, which reverses a preloaded magnetic shear, in the vicinity of the magnetic neutral line. The simulation results clearly indicated that the reversal of magnetic shear can cause a large-scale eruption of the magnetic arcade through a series of two different kinds of magnetic reconnections. The first reconnection is initiated by the resistive-tearing mode instability growing on the magnetic shear inversion layer and annihilates the sheared magnetic fluxes, which are oppositely directed along the magnetic neutral line. As a result of this, the magnetic arcade collapses into the reconnection point, and a new current sheet is generated above and below the shear inversion layer. The generation of new current sheets is followed by another magnetic reconnection, which drives the eruption of the sheared magnetic arcade. Mutual excitation of the two reconnections may explain the explosive property of the flare onset.

  136. The trigger mechanism of solar flares in a coronal arcade with reversed magnetic shear Reviewed

    K Kusano, T Maeshiro, T Yokoyama, T Sakurai

    ASTROPHYSICAL JOURNAL   Vol. 610 ( 1 ) page: 537 - 549   2004.7

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    Language:English   Publishing type:Research paper (scientific journal)   Publisher:UNIV CHICAGO PRESS  

    We have investigated the possibility that magnetic reconnection between oppositely sheared magnetic loops works as a trigger mechanism of solar flares, based on three-dimensional numerical simulations. The simulations were carried out by applying a slow footpoint motion, which reverses a preloaded magnetic shear, in the vicinity of the magnetic neutral line. The simulation results clearly indicated that the reversal of magnetic shear can cause a large-scale eruption of the magnetic arcade through a series of two different kinds of magnetic reconnections. The first reconnection is initiated by the resistive-tearing mode instability growing on the magnetic shear inversion layer and annihilates the sheared magnetic fluxes, which are oppositely directed along the magnetic neutral line. As a result of this, the magnetic arcade collapses into the reconnection point, and a new current sheet is generated above and below the shear inversion layer. The generation of new current sheets is followed by another magnetic reconnection, which drives the eruption of the sheared magnetic arcade. Mutual excitation of the two reconnections may explain the explosive property of the flare onset.

    DOI: 10.1086/421547

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  137. Simulation study of energy conversion process in magnetohydrodynamic turbulence due to magnetorotational instability Reviewed

    Junji Nakahara, Takahiro Miyoshi, Kanya Kusano

    Journal of the Physical Society of Japan   Vol. 73 ( 1 ) page: 94 - 101   2004.1

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    Language:English   Publishing type:Research paper (scientific journal)   Publisher:PHYSICAL SOC JAPAN  

    Three dimensional local simulation was performed to investigate the energy conversion and the dynamo action in the magnetohydrodynamic (MHD) turbulence due to the magnetorotational instability (MRI) in a differentially rotating disk, using Arbitrary Lagrangian Eulerian method. As a result, it was found that the turbulence plays a role to convert the magnetic energy to the kinetic energy, if the shear parameter q defined by -dln Ω/dln R is less than 2.3, where Ω and R are the angular velocity and the disk radius, respectively. It means that amplification of the magnetic energy in the MRI is mainly due to the twisting effect of differential rotation rather than a result of the turbulent dynamo action. When q ≥ 2.5, the energy conversion rate from the kinetic energy to the magnetic energy is switched to positive, because low modes, which are destabilized by the Rayleigh instability, can work for the turbulent dynamo. On the other hand, it is also revealed that, the α-dynamo effect exists at least for q ≥ 0.75, although the contribution to the amplification of the magnetic energy is very small. From these results, it can be concluded that, even though the MRI is able to amplify the magnetic energy, the turbulence due to the MRI is less effective as a driver of the conventional dynamo process, unless the Rayleigh instability arises. ©2004 The Physical Society of Japan.

    DOI: 10.1143/JPSJ.73.94

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  138. Magnetic helicity injection and sigmoidal coronal loops Reviewed

    TT Yamamoto, T Sakurai, K Kusano, T Maeshiro, T Yokoyama

    Solar-B Mission and the Forefront of Solar Physics, Proceedings   Vol. 325   page: 145 - 149   2004

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    We analyzed the magnetic helicity injection in NOAA Active Region 8011 with the method proposed by Kusano et al. (2002). It was found that the helical geometry of a sigmoidal loop in this region is consistent with the magnetic helicity injected from the foot points of the loop. We also made a statistical study of the correlation between X-ray intensity and magnetic helicity injection. We found that the sum of the absolute values of the magnetic helicity injection shows good correlation with the X-ray luminosity. The estimated flux of magnetic free energy injection is not highly correlated with the X-ray flux, because the former quantity is overestimated in our simple method.

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  139. Study of magnetic helicity in the solar corona Reviewed

    K Kusano, T Maeshiro, T Yokoyama, T Sakurai

    Solar-B Mission and the Forefront of Solar Physics, Proceedings   Vol. 325   page: 175 - 184   2004

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    Language:English   Publishing type:Research paper (international conference proceedings)   Publisher:ASTRONOMICAL SOC PACIFIC  

    Several new methodologies to detect the magnetic helicity injection activity across the photosphere into the solar corona have been developed recently. We briefly review the basic principle of the typical two methods, the so-called local correlation tracking (LCT) method and the induction equation (IE) method. The reliability of them is examined using a three-dimensional model field. The benchmark examination indicates that, if the vector magnetic field data are available, the IE method can greatly improve the accuracy of the helicity flux measurement. The physical implication of the recent results of the magnetic helicity measurement is also discussed. In particular, we emphasize the possibility that not only the intensity but also the complexity of the magnetic helicity injection from the photosphere could activate the energy liberation process in the solar corona.

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  140. Prospect for Multiple Time and Spatial Scale Simulation Research in Astrophysical Plasma Phenomena, Multiple Scale Simulation of Magnetic Reconnection Phenomena in the Solar Corona

    Kanya Kusano

    Journal of Plasma and Fusion Research     2003

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    DOI: 10.1585/jspf.79.496

  141. Effect of density stratification on the thermal convection in a rotating spherical shell Reviewed

    N. Nishikawa, K. Kusano

    Astrophysical Journal   Vol. 581 ( 1 I ) page: 745 - 759   2002.12

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    On the basis of the three-dimensional numerical simulation, we study the effect of density stratification on the thermal convection in a rotating spherical shell. Three different density-stratified equilibria, which have different polytropic indices, are adopted as the initial state of the simulation. The density ratio between the bottom and the top of the domain is in the range from 2.0 to 10.7, and the Taylor number is fixed to 104. It is found that when the Rayleigh number is slightly above the instability threshold, the convection structure is hardly affected by the difference of stratification, whereas when the Rayleigh number is much larger than the instability threshold, the nonlinear solution in the strongly stratified equilibria bifurcates into the sectorial convection and the quasi-axisymmetric zonal convection. Through the bifurcation from the sectorial solution to the quasi-axisymmetric solution, the sign of the averaged kinetic helicity is changed in each hemisphere (negative to positive in the northern hemisphere). The results suggest that the solar and the stellar convections must be sensitive to the density stratification.

    DOI: 10.1086/344138

    Scopus

  142. Measurement of magnetic helicity injection and free energy loading into the solar corona Reviewed

    K. Kusano, T. Maeshiro, T. Yokoyama, T. Sakurai

    Astrophysical Journal   Vol. 577 ( 1 I ) page: 501 - 512   2002.9

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    We develop a new methodology that can determine magnetic helicity flux as well as Poynting flux across the photosphere based on magnetograph observation. By applying this method, we study the injection mechanism of magnetic helicity and magnetic free energy into the solar corona. In order to derive the helicity and energy fluxes, first the velocity tangential to the solar surface is constructed by applying a correlation tracking technique on the magnetic observation, and second, the velocity component normal to the photosphere is derived from the condition that the magnetic evolution must be consistent with the induction equation. Through this procedure, we can determine the helicity and energy fluxes separately for the shear motion effect and for the flux emergence effect. Based on this new method, NOAA Active Region 8100 was analyzed from 1997 November 1 to 5 using data observed by the Solar and Heliospheric Observatory Michelson Doppler Interferometer and the vector magnetograph at the National Astronomical Observatory of Japan (NAOJ) in Tokyo. The results indicate that the photospheric shear motion and the flux emergence process have equally contributed to the helicity injection and have supplied magnetic helicity of opposite signs into this active region.

    DOI: 10.1086/342171

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  143. Measurement of Magnetic Helicity Injection and Free Energy Loading into the Solar Corona Reviewed

    Kusano,K., Maeshiro,T., Yokoyama,T. and Sakurai,T.

    The Astrophysical Journal   Vol. 577 ( 1 ) page: 501-512   2002.9

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    We develop a new methodology that can determine magnetic helicity flux as well as Poynting flux across the photosphere based on magnetograph observation. By applying this method, we study the injection mechanism of magnetic helicity and magnetic free energy into the solar corona. In order to derive the helicity and energy fluxes, first the velocity tangential to the solar surface is constructed by applying a correlation tracking technique on the magnetic observation, and second, the velocity component normal to the photosphere is derived from the condition that the magnetic evolution must be consistent with the induction equation. Through this procedure, we can determine the helicity and energy fluxes separately for the shear motion effect and for the flux emergence effect. Based on this new method, NOAA Active Region 8100 was analyzed from 1997 November 1 to 5 using data observed by the Solar and Heliospheric Observatory Michelson Doppler Interferometer and the vector magnetograph at the National Astronomical Observatory of Japan (NAOJ) in Tokyo. The results indicate that the photospheric shear motion and the flux emergence process have equally contributed to the helicity injection and have supplied magnetic helicity of opposite signs into this active region.

  144. Numerical study of three-dimensional magnetohydrodynamic instability in the solar coronal magnetic arcades Reviewed

    K. Kusano

    Astrophysical Journal   Vol. 571 ( 1 I ) page: 532 - 539   2002.5

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    Three-dimensional magnetohydrodynamic (MHD) instability in the solar coronal magnetic arcades, which are subject to the constant shearing motion at the feet, was investigated based on the numerical simulations. It was found that the magnetic arcade instability for three-dimensional modes undulating the magnetic arcade can grow if the aspect ratio (defined as the ratio of the arcade length to the width) is larger than unity. In particular, when the aspect ratio is much larger than unity, the nonlinear coupling among several modes dominates the dynamics. As a result, in a very long magnetic arcade, three-dimensional reconnection, which takes place in a limited region in the magnetic arcade, may proceed continuously.

    DOI: 10.1086/339910

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  145. Helicity injection into the solar corona Reviewed

    K Kusano, T Maeshiro, T Yokoyama, T Sakurai

    MULTI-WAVELENGTH OBSERVATIONS OF CORONAL STRUCTURE AND DYNAMICS   Vol. 13   page: 151 - 152   2002

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    Language:English   Publishing type:Research paper (international conference proceedings)   Publisher:PERGAMON-ELSEVIER SCIENCE LTD  

    We developed a new methodology to measure magnetic helicity as well as magnetic energy injection into the solar corona from magnetograph observations, and we studied the relationship between helicity injection and X-ray activity in the solar corona. In order to calculate the gauge-invariant helicity flux and the Poynting flux across the photosphere, first the velocity tangential to the photospheric surface is constructed by applying the correlation tracking technique on SOHO/MDI observations, and second the normal velocity is calculated by solving the induction equation as an inverse-problem using data from SOHO/MDI and the Solar Flare Telescope at NAOJ in Tokyo. The helicity injection as well as the free energy build-up is analyzed for active region NOAA 8100 from November 1 to 4, 1997. The results indicate that the emerging flux and the shear flow inject magnetic helicity of opposite sign (positive and negative, respectively) into the active region prior to a series of flares. Furthermore it is found that during the helicity injection process magnetic free energy in the amount of 5 x 1032 erg was supplied, which is much more than the X-ray flux emitted by the flares.

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  146. Numerical study of nonlinear forced magnetic reconnection Reviewed

    P. K. Browning, J. Kawaguchi, K. Kusano, G. E. Vekstein

    Physics of Plasmas   Vol. 8 ( 1 ) page: 132 - 138   2001.1

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    Two-dimensional numerical simulations are used to investigate nonlinear aspects of forced magnetic reconnection in a zero β highly conducting plasma. This is representative of the solar corona, where reconnection may be induced by external perturbations, e.g., at the photospheric boundary of the corona. The aim is to investigate the energy dissipation by the reconnection, which may provide a mechanism for heating the coronal plasma. The field is taken to he initially a sheared force-free equilibrium in a slab, and the effects of applying a slow deformation to the boundaries are investigated. Previous analytical studies assuming small departures from the initial equilibrium have found that a current sheet forms during an initial ideal phase of evolution, which subsequently relaxes to a reconnected equilibrium, releasing some magnetic energy. The linear theory predicts that the energy release has a singularity when the field is marginally stable to the tearing mode. The nonlinear evolution of the field is calculated numerically, focusing on the energy release. In particular, the strongly nonlinear behavior is studied in the parameter regime in which the linear theory breaks down. It is found that nonlinearities become strong close to the marginal stability point, and for such highly sheared fields, the energy released by reconnection is large even for weak boundary deformations. © 2001 American Institute of Physics.

    DOI: 10.1063/1.1329151

    Scopus

  147. Density stratification effects on the thermal convection in a rotating spherical shell Reviewed

    N Nishikawa, K Kusano

    RECENT INSIGHTS INTO THE PHYSICS OF THE SUN AND HELIOSPHERE: HIGHLIGHTS FROM SOHO AND OTHER SPACE MISSIONS   ( 203 ) page: 195 - 197   2001

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    The density stratification effects on the thermal convection in a rotating spherical shell, which is the representative of the solar convection zone, are investigated by three dimensional numerical simulations. It is found that, the convection structure in the strongly stratified system is switched from parallel cells aligned to the rotation axis to zonal rolles dominated by the longitudinally averaged mode, as the Rayleigh number increases much larger than the stability threshold. Corresponding to this structural transition, the averaged kinetic helicity reverses the sign in each hemisphere (from negative to positive in the northern hemisphere). The results indicate that the density stratification is much important for the nonlinear convection process in the rotating spherical shell.

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  148. Three-dimensional simulation study of magnetic reconnection in the solar corona Reviewed

    K Kusano

    EARTH PLANETS AND SPACE   Vol. 53 ( 6 ) page: 491 - 494   2001

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    Language:English   Publishing type:Research paper (scientific journal)   Publisher:TERRA SCIENTIFIC PUBL CO  

    A three-dimensional reconnection process, which is caused by the magnetic arcade instability, is investigated using numerical simulations. It is found that the aspect ratio (defined as the ratio of the length to the width of the magnetic arcade) is a crucial parameter to control the nonlinear dynamics. When the aspect ratio is rather small, the dynamics is governed by a symmetric mode, and more explosive reconnection happens. In a longer arcade, on the other hand, an undulating three-dimensional activity arises. It suggests that the variety in solar coronal activity may be caused by the differece in arcade shape.

    DOI: 10.1186/BF03353260

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  149. A global MHD simulation of the Jovian magnetosphere interacting with/without the IMF Reviewed

    Miyoshi, Takahiro, Kusano, Kanya

    Journal of Geophysical Research   Vol. 106 ( A6 ) page: 10723 - 10742   2001

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  150. A global MHD model of the Jovian magnetosphere Reviewed

    Miyoshi, Takahiro, Kusano, Kanya

    JAERI Research   Vol. 2000 ( 31 ) page: 1 - 47   2000

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  151. Simulation study on catastrophic instability in solar corona Reviewed

    K Kusano

    NUMERICAL ASTROPHYSICS   Vol. 240   page: 323 - 326   1999

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  152. Magnetic helicity and stability in solar corona Reviewed

    K. Kusano

    Geophysical Monograph Series   Vol. 111   page: 149 - 156   1999

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    Language:English   Publishing type:Part of collection (book)   Publisher:Blackwell Publishing Ltd  

    Solar coronal magnetic field plays a role as a channel through which the magnetic helicity is transported from the sun into the interplanetary space. If the coronal field forms the arcades, and if the magnetic Reynolds number is sufficiently large, the helicity transportation proceeds intermittently, even in the case that the helicity is constantly supplied from the sun. The intermittent transportation is a cyclic process which consists of the helicity storage, magnetic reconnection, and the plasmoid ejection. It is a result of the competition between the destabilization by the photospheric activity and the spontaneous stabilization caused by the magnetic arcade instability. The total helicity is well conserved even in the energy relaxation process, so that Taylor’s hypothesis on the selective dissipation is applicable also to the solar corona. However, the numerical simulations indicate that the energy relaxation is even partial, and that the free energy cannot be exhausted, because the photospheric boundary gives a stronger constraint than Taylor’s theory predicted. The coronal field could evolve around the marginally stable limit, which locates in the intermediate region between the stable and the unstable linear force free solutions. The results suggest that, even if there is no external trigger, the coronal plasma is able to generate intermittent activities like flares.

    DOI: 10.1029/GM111p0149

    Scopus

  153. Bifurcation-transition dynamics in solar coronal plasma Reviewed

    K Kusano

    OBSERVATIONAL PLASMA ASTROPHYSICS: FIVE YEARS OF YOHKOH AND BEYOND   Vol. 229   page: 185 - 186   1998

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  154. Wave propagation in 2-fluid dusty plasma system Reviewed

    T Takaishi, K Kusano

    PHYSICS OF DUSTY PLASMAS   Vol. 446   page: 111 - 115   1998

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    The propagation of electro-static waves in a-fluid dusty plasma system is investigated. We study the dynamics of the dust particles and ions in the a-fluid dusty plasma system. We find that the electro-static waves in dusty plasma are developed as the new modes. When we assume that the charge-up process in the equilibrium can be eliminated, these modes approach to Ion-Acoustic mode (Q(d0) = 0) Or Dust-ion-Acoustic mode (P-d0 = 0).

    Web of Science

  155. Simulation study on magneto-gravity instabilities in magnetic shear field

    Moriyama, Katsushi, Kusano, Kanya, Miyoshi, Takahiro

    Observational Plasma Astrophysics - Five Years of Yohkoh and Beyond     page: 331 - 332   1998

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  156. Nonlinear dynamics of magnetic buoyancy instabilities in a sheared magnetic field Reviewed

    K. Kusano, K. Moriyama, T. Miyoshi

    Physics of Plasmas   Vol. 5 ( 7 ) page: 2582 - 2589   1998

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    Nonlinear dynamics of magnetic buoyancy instabilities for the Parker-type and interchange-type modes are numerically investigated with the aim of understanding the emerging mechanism of solar coronal magnetic loops. Two-dimensional nonlinear magnetohydrodynamic (MHD) simulations of the magnetic buoyancy instabilities are performed in a highly stratified domain consisting of two temperature regions corresponding to the corona and the chromosphere, respectively. First, it is revealed that the angle between the wave vector and the magnetic field at the top interface of the magnetic layer is a crucial parameter controlling the basic properties of the instability. Second, it is found that the magnetic buoyancy instability in the sheared field grows nonlinearly larger than in the shearless field, although the magnetic shear reduces the linear growth rate. This is due to the Parker-type mode being destabilized by the nonlinear effect of the interchange-type instabilities. Third, it is shown that the magnetic buoyancy instability can drive magnetic reconnections which create isolated flux regions. © 1998 American Institute of Physics.

    DOI: 10.1063/1.872944

    Scopus

  157. A global magnetohydrodynamic simulation of the Jovian magnetosphere Reviewed

    T Miyoshi, K Kusano, K Nishikawa

    ICPP 96 CONTRIBUTED PAPERS - PROCEEDINGS OF THE 1996 INTERNATIONAL CONFERENCE ON PLASMA PHYSICS, VOLS 1 AND 2     page: 526 - 529   1997

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    Language:English   Publishing type:Research paper (international conference proceedings)   Publisher:JAPAN SOCIETY PLASMA SCIENCE &NUCLEAR FUSION RESEARCH  

    Three-dimensional global magnetohydrodynamic (MHD) simulations are performed in order to investigate the global structure and the dynamics of the Jovian magnetosphere. Particularly, we investigate the influence of the planetary rotation onto the magnetospheric structure. The effects of the interplanetary magnetic field (IMF) in the solar wind are also considered. The simulation results clearly indicate that the dawn-dusk asymmetries are generated due to the effect of the planetary rotation. The plasmoid can be also observed in the tail region. The neutral lines of the magnetic field, however, appear obliquely from the dawn-dusk line, so that the location of the plasmoid is quite different from that in the Earth's magnetosphere.

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  158. Generation and evolution of solar coronal magnetic loops Reviewed

    K Moriyama, K Kusano, T Miyoshi, K Nishikawa

    ICPP 96 CONTRIBUTED PAPERS - PROCEEDINGS OF THE 1996 INTERNATIONAL CONFERENCE ON PLASMA PHYSICS, VOLS 1 AND 2     page: 1006 - 1009   1997

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    We perform the tyro-dimensional magnetohydrodynamic (MHD) simulation which can calculate either the generation and the evolution of the solar coronal magnetic loops with a magnetic shear. The linear stability analysis reveals that, if the magnetic field has a stronger shear, higher-wavenumber perturbations are destabilized because of the excitation of the interchange mode, so that the unstable region in the wavenumber space is enlarged. In the nonlinear simulation, it is observed that as the result of the initial perturbation growing, the magnetic flux emerges into the corona and the coronal loop is generated, It is also observed that when the perturbation of the short-wavelength is imposed to the strongly sheared magnetic held. the isolated flux tube is generated through the magnetic reconnection process.

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  159. Three dimensional simulation study of the magnetohydrodynamic relaxation process in the solar corona Reviewed

    Y Suzuki, K Kusano, K Nishikawa

    ICPP 96 CONTRIBUTED PAPERS - PROCEEDINGS OF THE 1996 INTERNATIONAL CONFERENCE ON PLASMA PHYSICS, VOLS 1 AND 2     page: 1582 - 1585   1997

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    Language:English   Publishing type:Research paper (international conference proceedings)   Publisher:JAPAN SOCIETY PLASMA SCIENCE &NUCLEAR FUSION RESEARCH  

    The magnetohydrodynamic (MHD) relaxation process in the solar coronal magnetic field is investigated in terms of three-dimensional numerical simulations. We consider the dynamics of magnetic loops, which is caused by the photospheric twisting motion. It is found that, as a result of the rising of the magnetic loops, isolated flux tubes (plasmoids) are generated on top of the loops through the magnetic reconnection process. It is revealed that the plasmoid formation can be explained as a transition between two different solutions of the Woltjer-Taylor minimum energy state. (Kusano, Suzuki, & Nishikawa 1995). Furthermore, the three-dimensional effect in the transition dynamics is investigated in detail by the Fourier mode analysis.

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  160. Simulation study on reversed field pinch plasmas with RF current drive Reviewed

    T Nagai, K Kusano, Y Kondoh, S Shiina, K Nishikawa

    ICPP 96 CONTRIBUTED PAPERS - PROCEEDINGS OF THE 1996 INTERNATIONAL CONFERENCE ON PLASMA PHYSICS, VOLS 1 AND 2     page: 1042 - 1045   1997

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    Language:English   Publishing type:Research paper (international conference proceedings)   Publisher:JAPAN SOCIETY PLASMA SCIENCE &NUCLEAR FUSION RESEARCH  

    We study the relaxation phenomena of the reversed field pinch (RFP) plasma with a radio-frequency (rf) current drive. We develop the magnetohydrodynamic code, in which the effect of the rf current drive is included in the induction equation as an external electric field obtained from the ray tracing of the fast magnetosonic wave. As the results of simulations, we observe that the rf current drive can effectively reduce the disturbance due to the kink mode instabilities and it may sustain the reversed held without the MHD relaxation dynamics, These results suggest that the rf current drive is a prospective method to enable a quiet sustainment of the RFP configuration.

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  161. Self-organization in solar coronal plasma Reviewed

    K Kusano, Y Suzuki, K Nishikawa

    ICPP 96 CONTRIBUTED PAPERS - PROCEEDINGS OF THE 1996 INTERNATIONAL CONFERENCE ON PLASMA PHYSICS, VOLS 1 AND 2     page: 1586 - 1589   1997

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    Language:English   Publishing type:Research paper (international conference proceedings)   Publisher:JAPAN SOCIETY PLASMA SCIENCE &NUCLEAR FUSION RESEARCH  

    The theoretical proposition, that solar hares are self-organization processes to realize the Taylor's minimum energy state [K.Kusano, ct al., Astrophys. J., 441 942 (1995)], is examined by the numerical simulations. The simulation shows that the self-organization process indeed takes place, and that a rapid energy relaxation process is achieved through magnetic reconnection on thin current sheets, as expected from the theory. However, it is also clarified that, since the line-tied condition on the photosphere severely restricts the energy relaxation in addition to Taylor's hypothesis on total helicity conservation. Furthermore, we consider the storage mechanism of the free energy to drive solar flares, and find that a substantial free energy can be stored in the coronal magnetic field through a competitive process between the helicity injection due to the photospheric motion and the instability in the coronal arcade system.

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  162. Magnetic reconnection in solar corona Reviewed

    K Kusano, K Nishikawa

    ICPP 96 CONTRIBUTED PAPERS - PROCEEDINGS OF THE 1996 INTERNATIONAL CONFERENCE ON PLASMA PHYSICS, VOLS 1 AND 2     page: 494 - 497   1997

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    Language:English   Publishing type:Research paper (international conference proceedings)   Publisher:JAPAN SOCIETY PLASMA SCIENCE &NUCLEAR FUSION RESEARCH  

    Magnetic reconnection, which arises from the nonlinearity of the magnetohydrodynamic instability in the solar coronal loops, is analyzed in detail by the numerical simulations. It is revealed that the time-scale of the current sheet formation does not depend on the linear growth rate of the initial instability, and it is scaled by the Alfven transit times. It is also found that! when the magnetic Reynolds number is in the range from 10(3) to 10(4), the length of the current layer in the reconnection site is geometrically limited to the scale of the loop feet interval and is hardly affected by the change in the resistivity. Consequently, the width of the current layer is proportional to the square root of the resistivity.

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  163. Three-dimensional simulation of a compressible magnetoconvection Reviewed

    S Kawasaki, K Kusano, T Miyoshi, K Nishikawa

    ICPP 96 CONTRIBUTED PAPERS - PROCEEDINGS OF THE 1996 INTERNATIONAL CONFERENCE ON PLASMA PHYSICS, VOLS 1 AND 2     page: 966 - 969   1997

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    Language:English   Publishing type:Research paper (international conference proceedings)   Publisher:JAPAN SOCIETY PLASMA SCIENCE &NUCLEAR FUSION RESEARCH  

    The three-dimensional (3D) compressible magnetoconvection in a rectangular domain with a horizontal magnetic field is investigated using the numerical simulation. The 3D calculations are carried out adopting the result from the two-dimensional convection simulations as the initial condition. It is observed that the stable roll convection in the 2D system is unstable in the 3D system, and a complex spatial-temporal structure is generated.

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  164. On self-consistent stationary propagation of relativistically coupled electromagnetic and electrostatic waves. II. Effects of electron-positron pair creation Reviewed

    Levan N. Tsintsadze, Kanya Kusano, Kyoji Nishikawa

    Physics of Plasmas   Vol. 4 ( 4 ) page: 911 - 916   1997

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    Language:English   Publishing type:Research paper (scientific journal)   Publisher:American Institute of Physics Inc.  

    Effects of electron-positron pair creation on the stationary one-dimensional propagation of relativistically coupled electromagnetic and electrostatic waves are studied based on the self-consistent model presented in the previous paper for an electron-ion plasma [L. N. Tsintsadze and K. Nishikawa, Phys. Plasmas 3, 511 (1996)]. The pair-created particles are treated as a cold electron-positron plasma at their creation point. In addition to the results similar to those obtained for the electron-ion plasma, a new type of instability of the finite amplitude plane wave is found which is purely growing in the wave frame near threshold. A novel solution describing an envelope shock which represents a wake-field excitation by a solitary electromagnetic pulse is obtained by taking into account the trapping of the pair-created particles in the upstream region. © 1997 American Institute of Physics.

    DOI: 10.1063/1.872207

    Scopus

  165. MHD simulation of a rapidly rotating magnetosphere interacting with the external plasma flow Reviewed

    T. Miyoshi, K. Kusano

    Geophysical Research Letters   Vol. 24 ( 21 ) page: 2627 - 2630   1997

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    Language:English   Publishing type:Research paper (scientific journal)   Publisher:American Geophysical Union  

    The nonlinear interaction of a rapidly rotating magnetosphere with the external supersonic plasma flow is investigated by using the three-dimensional global magneto-hydrodynamic (MHD) simulation. The results of the simulations clearly indicate that various dawn-dusk asymmetries are generated due to the effect of the rotation. Particularly, the location of the plasmoid, which is generated in the tail region of the rotating magnetosphere, is quite different from the case without rotation. It is also found that distinctive magnetospheric structures such as the plasma disc are largely modified in response to the dynamic pressure in the external plasma flow. Copyright 1997 by the American Geophysical Union.

    DOI: 10.1029/97GL52739

    Scopus

  166. Three dimensional simulation study of the magnetohydrodynamic relaxation process in the solar corona

    Y Suzuki, K Kusano, K Nishikawa

    MAGNETODYNAMIC PHENOMENA IN THE SOLAR ATMOSPHERE     page: 587-588   1996

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  167. Activities of INSAM in Hiroshima University Reviewed

    Shinji Hioki, Satoru Honda, Masasi Inoue, Kanya Kusano, Osamu Miyamura, Masahisa Tabata

    Progress of Theoretical Physics Supplement   ( 122 ) page: 51 - 56   1996

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    Language:English   Publishing type:Research paper (scientific journal)   Publisher:Yukawa Institute for Theoretical Physics  

    INSAM (Institute for Numerical Simulations and Applied Mathematics) in Hiroshima University is a group consists of researchers whose major are Numerical Simulations and/or Applied Mathematics. It covers wide range of science: mathematics, physics, chemistry, biology and earth &amp
    planetary system. In this report the current activities of INSAM are presented. The performance of Intel Paragon, which is a main computer resource of INSAM, and its implementation for our applications will be also discussed.

    DOI: 10.1143/PTPS.122.51

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  168. Bifurcation and stability of the coronal magnetic field Reviewed

    K Kusano, Y Suzuki, K Moriyama, K Fujie, K Nishikawa

    MAGNETODYNAMIC PHENOMENA IN THE SOLAR ATMOSPHERE     page: 303 - 304   1996

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    Language:English   Publishing type:Research paper (international conference proceedings)   Publisher:KLUWER ACADEMIC PUBL  

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  169. Three dimensional simulation study of the magnetohydrodynamic relaxation process in the solar corona Reviewed

    Y Suzuki, K Kusano, K Nishikawa

    MAGNETODYNAMIC PHENOMENA IN THE SOLAR ATMOSPHERE     page: 587 - 588   1996

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    Language:English   Publishing type:Research paper (international conference proceedings)   Publisher:KLUWER ACADEMIC PUBL  

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  170. A solar flare triggering mechanism based on the Woltjer-Taylor minimum energy principle Reviewed

    K. Kusano, Y. Suzuki, K. Nishikawa

    Astrophysical Journal   Vol. 441 ( 2 ) page: 942 - 951   1995.3

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    Language:English   Publishing type:Research paper (scientific journal)   Publisher:Institute of Physics Publishing  

    The general solution of the Woltjer-Taylor minimum energy state is found in the solar coronal geometry, which is modeled as a rectangular domain. It is shown that the solution bifurcates into two different states when the magnetic helicity integral or the geometrical factor defined as the ratio of the height to the width of the domain is satisfactorily increased. Based on this analysis, it is theoretically proposed that a solar flare is a transition process between two different Woltjer-Taylor states, which are generated as a result of the bifurcation. The theory predicts that a solar flare is triggered when the vertical size of the coronal magnetic loop becomes longer than the horizontal size. The topological structure in the coronal magnetic field must be dramatically changed in the transition process. The result implies that in general, magnetic reconnection must be accompanied by a solar flare. The numerical simulation shows that the transition process is dynamically realized as a result of a twisting motion on the photosphere. Based on this theory, disagreements among recent simulation works on the plasmoid formation problem can be consistently explained.

    DOI: 10.1086/175413

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  171. A SOLAR-FLARE TRIGGERING MECHANISM-BASED ON THE WOLTJER-TAYLOR MINIMUM ENERGY PRINCIPLE Reviewed

    KUSANO K, SUZUKI Y, NISHIKAWA K

    The Astrophysical Journal   Vol. 441 ( 2 ) page: 942-951   1995.3

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    Authorship:Lead author   Language:English   Publishing type:Research paper (scientific journal)  

    The general solution of the Woltjer-Taylor minimum energy state is found in the solar coronal geometry, which is modeled as a rectangular domain. It is shown that the solution bifurcates into two different states when the magnetic helicity integral or the geometrical factor defined as the ratio of the height to the width of the domain is satisfactorily increased. Based on this analysis, it is theoretically proposed that a solar flare is a transition process between two different Woltjer-Taylor states, which are generated as a result of the bifurcation. The theory predicts that a solar flare is triggered when the vertical size of the coronal magnetic loop becomes longer than the horizontal size. The topological structure in the coronal magnetic field must be dramatically changed in the transition process. The result implies that in general, magnetic reconnection must be accompanied by a solar flare. The numerical simulation shows that the transition process is dynamically realized as a result of a twisting motion on the photosphere. Based on this theory, disagreements among recent simulation works on the plasmoid formation problem can be consistently explained.

  172. Energy conversion processes in the starting-up phase of externally driven reconnection Reviewed

    Kanya Kusano, Yoshio Suzuki, Tetsuya Sato, Kyoji Nishikawa

    Physics of Fluids B   Vol. 5 ( 2 ) page: 357 - 364   1993

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    Language:English   Publishing type:Research paper (scientific journal)  

    The energy conversion process as well as the plasma heating mechanism in the starting-up phase of driven reconnection is investigated in detail using two-dimensional magnetohydrodynamic (MHD) simulation. It is revealed that the compressional heating effect is predominant in this phase rather than the Ohmic and the viscous heating. The predominance of the compressional heating means that the plasma flow energy is considerably converted to the thermal energy. The strong compression takes place in the process during which the fast shock is generated in the downstream region of the reconnection point. The plasma heating due to nonsteady reconnection is briefly discussed as a promising mechanism for the anomalous ion heating, which is observed in reversed-field pinch (RFP) experiments. © 1993 American Institute of Physics.

    DOI: 10.1063/1.860521

    Scopus

  173. Role of compressibility on driven magnetic reconnection Reviewed

    T. Sato, T. Hayashi, K. Watanabe, R. Horiuchi, M. Tanaka, N. Sawairi, K. Kusano

    Physics of Fluids B   Vol. 4 ( 2 ) page: 450 - 457   1992

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    Whether it is induced by an ideal (current driven) instability or by an external force, plasma flow causes a change in the magnetic field configuration and often gives rise to a current intensification locally, thereby a fast driven reconnection being driven there. Many dramatic phenomena in magnetically confined plasmas such as magnetospheric substorms, solar flares, magnetohydrodynamic (MHD) self-organization, and tokamak sawtooth crash, may be attributed to this fast driven reconnection. Using a fourth-order MHD simulation code it is confirmed that compressibility of the plasma plays a crucial role in leading to a fast (MHD time scale) driven reconnection. This indicates that the incompressible representation is not always applicable to the study of a global dynamical behavior of a magnetically confined plasma. © 1992 American Institute of Physics.

    DOI: 10.1063/1.860295

    Scopus

  174. Computer Simulation-Trends in Highly Nonlinear Physics. 2. Macroscopic Nonlinear Phenomena. 2-2. Nonlinear Physics in Reversed-Field Pinch.

    Kusano Kanya

    Journal of Plasma and Fusion Research   Vol. 65 ( 5 ) page: 528 - 543   1991

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    Language:Japanese   Publishing type:Research paper (scientific journal)   Publisher:The Japan Society of Plasma Science and Nuclear Fusion Research  

    The computer simulation has played an important role for the research of reversed-field pinch (REP) physics. Especially, in order to elucidate essential nonlinear mechanisms, the simulation study is a much useful methodology. It is described how the computer simulation has been applied to solve the self-reversal and the self-sustainment processes.

    DOI: 10.1585/jspf1958.65.528

    CiNii Books

    Other Link: https://jlc.jst.go.jp/DN/JALC/00009529311?from=CiNii

  175. Mhd simulation of the toroidal phase locking mechanism in a reversed field pinch plasma Reviewed

    K. Kusano, T. Tamano, T. Sato

    Nuclear Fusion   Vol. 31 ( 10 ) page: 1923 - 1932   1991

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    The toroidal phase locking process of kink modes in a reversed field pinch (RFP) plasma is investigated in detail by means of magnetohydrodynamic (MHD) simulation. The physical mechanism of phase locking is clarified. The two most dominant linearly unstable kink modes govern the evolution of other kink modes, whereby phase locking takes place. It is confirmed that the phase locking process is not a special phenomenon of plasmas with a resistive boundary, but a common feature of the MHD relaxation process in RFPs. The relation between the phase locking process and the MHD relaxation process is briefly discussed. It is found that phase locking is reproduced cyclically in the sustainment process. © 1991, IOP publishing Ltd.

    DOI: 10.1088/0029-5515/31/10/010

    Scopus

  176. SIMULATION STUDY OF THE SELF-SUSTAINMENT MECHANISM IN THE REVERSED-FIELD PINCH CONFIGURATION Reviewed

    KUSANO K, SATO T

    NUCLEAR FUSION   Vol. 1990 ( 10 ) page: 2075-2096   1990.10

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  177. Simulation Study of Self-Organization and Self-Relaxation Processes in Plasma : Complex Dynamics in Nonlinear Systems :

    HORIUCHI Ritoku, KUSANO Kanya, WATANABE Kunihiko, HAYASHI Takaya, SATO Tetsuya, NISHIKAWA Kyoji

    Progress of theoretical physics. Supplement   ( 99 ) page: 206 - 219   1990

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    Language:English   Publishing type:Research paper (scientific journal)   Publisher:Progress of Theoretical Physics  

    Recent progress in super-computers has opened a new tool for the study of nonlinear dynamics in plasmas. This paper reviews the recent computer simulation studies for the self-organization and self-relaxation processes in MHD plasmas carried out by the Hiroshima group. Taylor's conjecture for the selective dissipation of magnetic energy keeping the total magnetic helicity canstant is confirmed and the mechanisms for formation and maintenance of the reversed field pinch configuration are explained in terms of the self-relaxation of the plasma due to a driven magnetic reconnection triggered by ideal MHD helical kink unstable modes and their nonlinear couplings.

    DOI: 10.1143/PTPS.99.206

    CiNii Books

    Other Link: http://dl.ndl.go.jp/info:ndljp/pid/10883515

  178. SYNTHESIS OF NEW CATIONIC BINAP-RUTHENIUM(II) COMPLEXES AND THEIR USE IN ASYMMETRIC HYDROGENATION [BINAP = 2,2'-BIS(DIPHENYLPHOSPHINO)-1,1'-BINAPHTHYL]

    MASHIMA K, KUSANO KH, OHTA T, NOYORI R, TAKAYA H

    JOURNAL OF THE CHEMICAL SOCIETY-CHEMICAL COMMUNICATIONS   ( 17 ) page: 1208-1210   1989.9

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    Web of Science

  179. Global and local relaxations in magnetohydrodynamic plasmas Reviewed

    Tetsuya Sato, Ritoku Horiuchi, Kanya Kusano

    Physics of Fluids B   Vol. 1 ( 1 ) page: 255 - 257   1989

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    Based on theoretical and computational considerations, it is confirmed that magnetic reconnection driven nonlinearly by a kink instability plays a key role in the magnetohydrodynamic relaxation. An important finding is that the relaxation takes the form of either global relaxation (e.g., the reversed field pinch relaxation) or local relaxation (e.g., the tokamak sawtooth relaxation), depending on whether the driven reconnection is total (antiparallel) or partial (partially antiparallel). © 1988 American Institute of Physics.

    DOI: 10.1063/1.859100

    Scopus

  180. Simulation study of ultra-low-q discharge process Reviewed

    K. Kusano, T. Sato, H. Yamada, Y. Murakami, Z. Yoshida, N. Inoue

    Nuclear Fusion   Vol. 28 ( 1 ) page: 53 - 72   1988

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    The sixth order wave equation which results from a finite temperature expansion of the Vlasov equation is solved globally in the ion cyclotron range of frequencies. A perpendicularly stratified, onedimensional slab plasma is assumed. The diamagnetic drift and the associated anisotropy are included in the unperturbed distribution function to ensure a self-adjoint system. All x-dependence in the plasma pressure and magnetic field is retained along with the electric field parallel to B. Thus, Landau damping of the ion Bernstein wave is included self-consistently. Because of the global nature of the solution, the evanescent short wavelength Bernstein waves do not grow exponentially as in shooting methods. Strong variations occur in the absorption and in the structure of the wave fields as resonance topology is varied. Solutions to the complete sixth order differential equation are compared to those from an approximate second order equation based on local dispersion theory. © 1988 IOP Publishing Ltd.

    DOI: 10.1088/0029-5515/28/1/007

    Scopus

  181. SPONTANEOUS FORMATION OF MAGNETOHYDRODYNAMIC EQUILIBRIUM PROFILES - TOKAMAKS, REVERSED-FIELD PINCHES, AND THEIR INTERMEDIATES

    Z YOSHIDA, K KUSANO, N INOUE

    PHYSICS OF FLUIDS   Vol. 30 ( 8 ) page: 2465 - 2469   1987.8

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    Language:English   Publishing type:Research paper (scientific journal)   Publisher:AMER INST PHYSICS  

    DOI: 10.1063/1.866085

    Web of Science

  182. NONLINEAR COUPLING EFFECTS ON THE RELAXATION PROCESS IN THE REVERSED FIELD PINCH Reviewed

    KUSANO K, SATO T

    NUCLEAR FUSION   Vol. 27 ( 5 ) page: 821-832   1987.5

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  183. Letters:Observation of ultra low q equilibrium Reviewed

    H. Yamada, K. Kusano, Y. Kamada, M. Utsumi, Z. Yoshida, N. Inoue

    Nuclear Fusion   Vol. 27 ( 7 ) page: 1169 - 1173   1987

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    The characteristics of a toroidal discharge with qa ≈ 1/2 is studied on TORIUT-6. Ultra low q equilibria that are stable against the global kink mode are realized through MHD relaxation and are shown to be characterized by dq/dr &lt
    0 and a hollow current profile. The stable state lasts for 600 μs, which is of the order of the classical diffusion time. These experimental observations are consistent with non-linear MHD simulation results. © IOP Publishing Ltd.

    DOI: 10.1088/0029-5515/27/7/010

    Scopus

  184. SIMULATION STUDY OF THE SELF-REVERSAL PROCESS IN THE REVERSED-FIELD PINCH BASED ON A NONLINEARLY DRIVEN RECONNECTION MODEL Reviewed

    KUSANO, K; SATO, T

    NUCLEAR FUSION   Vol. 26 ( 8 ) page: 1051-1061   1986.8

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  185. Nonlinear driven reconnection in the reversed-field pinch Reviewed

    Tetsuya Sato, Kanya Kusano

    Physical Review Letters   Vol. 54 ( 8 ) page: 808 - 810   1985

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    We propose a theory that a new type of magnetic reconnection, nonlinear driven reconnection, is triggered during the nonlinear development of an m=1 helical kink-mode instability. This reconnection process can well explain nonlinear reconnection observed in the previous simulation and can be a candidate for the self-reversal mechanism in the reversed-field pinch. © 1985 The American Physical Society.

    DOI: 10.1103/PhysRevLett.54.808

    Scopus

▼display all

Books 31

  1. 地球・惑星・生命 = The earth, planets, and life

    日本地球惑星科学連合( Role: Sole author ,  4 宇宙天気予報とは何か(草野完也))

    東京大学出版会  2020  ( ISBN:9784130637152

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    Total pages:xii, 264, 8p   Language:Japanese

    CiNii Books

  2. Extreme Solar Particle Storms: The hostile Sun

    K Kusano, E Cliver, H Hayakawa, G A Kovaltsov, I G Usoskin( Role: Joint author ,  CHAPTER 2 What Can Be Learned from Modern Data? K Kusano, E Cliver, H Hayakawa, G A Kovaltsov and I G Usoskin)

    IOP Publishing Ltd  2019  ( ISBN:9780750322324

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    Language:Japanese

  3. Long-term datasets for the understanding of solar and stellar magnetic cycles : proceedings of the 340th Symposium of the International Astronomical Union held in Jaipur, India, February 19-23, 2018

    International Astronomical Union. Symposium, Banerjee, Dipankar, Jiang, Jie, 草野, 完也, Solanki, Sami K.( Role: Sole author)

    Cambridge University Press  2018  ( ISBN:9781108471091

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    Total pages:xx, 331 p.   Language:English

    CiNii Books

  4. シリーズ現代の天文学 10太陽

    ( Role: Joint author)

    日本評論社  2009.3 

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  5. 現代の天文学 第10巻「太陽」

    草野 完也( Role: Sole author)

    日本評論社  2009 

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    Language:Japanese

  6. Multi-Structure DynamicsUniversal Law in the Life, Space, and Earth Science

    Sakaguchi, H., Kusano, K., Suetsugu, D.( Role: Joint author)

    University of Tokyo Press  2008.3 

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    Language:Japanese

  7. 階層構造の科学

    草野 完也( Role: Sole author)

    東京大学出版会  2008  ( ISBN:9784130603065

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  8. Reconnection of Magnetic FieldsMagnetohydrodynamics and Collisionless Theory and Observations

    ( Role: Joint author)

    Cambridge University Press  2007 

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    Language:English

  9. Reconnection of Magnetic Fields: MHD and Collisionless Theory and Applications to the Sun and Magnetosphere

    ( Role: Sole author)

    Cambridge University Press  2007  ( ISBN:9780521854207

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  10. 太陽および宇宙プラズマにおける磁気ヘリシティのダイナミクスに関する研究

    草野, 完也( Role: Sole author)

    [海洋研究開発機構・地球シミュレータセンター]  2007 

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    Total pages:178p   Language:Japanese

    CiNii Books

  11. Helicity Injection into the Solar Corona

    ( Role: Sole author)

    Multi-Wavelength Observations of Coronal Structure and Dynamics, Yohkoh 10th Anniversary Meeting, COSPAR Colloquia Series, Pergamon  2002 

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    Language:Japanese

  12. Helicity Injection into the Solar Corona

    ( Role: Sole author)

    Multi-Wavelength Observations of Coronal Structure and Dynamics, Yohkoh 10th Anniversary Meeting, COSPAR Colloquia Series, Pergamon  2002 

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    Language:Japanese

  13. Effect of Density Stratification on the Thermal Convection in a Rotating Spherical Shell

    ( Role: Sole author)

    ASP Conference Series  2001 

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    Language:Japanese

  14. Effects of Density Stratification on the thermal Convection in Rotating Spherical Shell(共著)

    草野 完也( Role: Sole author)

    Recent Insights into the Physics of the Sun and Heliosphere Highlights from SOHO and Other Space Mission(The Astronomical Society of the Pacific)  2001 

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    Language:Japanese

  15. Effect of Density Stratification on the Thermal Convection in a Rotating Spherical Shell

    ( Role: Sole author)

    ASP Conference Series  2001 

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    Language:Japanese

  16. Effects of Density Stratification on the thermal Convection in Rotating Spherical Shell(共著)

    ( Role: Sole author)

    Recent Insights into the Physics of the Sun and Heliosphere Highlights from SOHO and Other Space Mission(The Astronomical Society of the Pacific)  2001 

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    Language:Japanese

  17. Effect of Density Stratification on the Thermal Convection in a Rotating Spherical Shell

    ( Role: Sole author)

    ASP Conference Series  2001 

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    Language:Japanese

  18. Magnetic Helicity and Stability in Solar Corona

    ( Role: Sole author)

    Magnetic Helicity in Space and Laboratory Plasmas Geophysical Monograph (]G0003[)(American Geophysical Union)  1999 

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    Language:Japanese

  19. Magnetic Helicity and Stability in Solar Corona

    ( Role: Sole author)

    Magnetic Helicity in Space and Laboratory Plasmas Geophysical Monograph (]G0003[)(American Geophysical Union)  1999 

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  20. Wave Propagation in 2-Fluid Dusty Plasma System(共著)

    ( Role: Sole author)

    Physics of Dusty Plasmas(American Institute of Physics)  1998 

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    Language:Japanese

  21. Bifurcation-Transition Dynamics in Solar Coronal Plasma

    ( Role: Sole author)

    Observational Plasma Astrophysics : Five Years of Yohkoh and Beyond(Kluwer Academic)  1998 

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  22. Wave Propagation in 2-Fluid Dusty Plasma System(共著)

    ( Role: Sole author)

    Physics of Dusty Plasmas(American Institute of Physics)  1998 

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    Language:Japanese

  23. Simulation Study on Magneto-Gravity Instabilities in Magnetic Shear Field(共著)

    ( Role: Sole author)

    Observational Plasma Astrophysics : Five Years of Yohkoh and Beyond(Kluwer Academic)  1998 

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    Language:Japanese

  24. Simulation Study on Magneto-Gravity Instabilities in Magnetic Shear Field(共著)

    ( Role: Sole author)

    Observational Plasma Astrophysics : Five Years of Yohkoh and Beyond(Kluwer Academic)  1998 

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    Language:Japanese

  25. Bifurcation-Transition Dynamics in Solar Coronal Plasma

    ( Role: Sole author)

    Observational Plasma Astrophysics : Five Years of Yohkoh and Beyond(Kluwer Academic)  1998 

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    Language:Japanese

  26. Bifurcation and Stability of the coronal magnetic field

    ( Role: Sole author)

    Proc. the IAU Colloquium No. 153, Phenomena in the Solar Atmosphere, Klucner Academic  1995 

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    Language:Japanese

  27. Bifurcation and Stability of the coronal magnetic field

    ( Role: Sole author)

    Proc. the IAU Colloquium No. 153, Phenomena in the Solar Atmosphere, Klucner Academic  1995 

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    Language:Japanese

  28. Simulation Study of Self-Sustainment Mechanism for the Reversed-Field Pinch Confeguration

    ( Role: Sole author)

    Edi trice Composition  1989 

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    Language:Japanese

  29. Simulation Study of Self-Sustainment Mechanism for the Reversed-Field Pinch Confeguration

    ( Role: Sole author)

    Edi trice Composition  1989 

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    Language:Japanese

  30. Simulation Study of Relaxation Processes in Toroidal Plasmas

    ( Role: Sole author)

    World Scientific  1987 

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    Language:Japanese

  31. Simulation Study of Relaxation Processes in Toroidal Plasmas

    ( Role: Sole author)

    World Scientific  1987 

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▼display all

MISC 109

  1. 太陽活動による地球環境変動の解明 Invited Reviewed

    草野完也, 堀田英之

    日本シミュレーション学会誌「シミュレーション」   Vol. 39 ( 2 )   2020

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  2. 2.Understanding Space Climate:Current Status and Open Issues Invited

    Kanya Kusano

      Vol. 90 ( 2 ) page: 107 - 111   2014.2

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    CiNii Books

    Other Link: http://dl.ndl.go.jp/info:ndljp/pid/10459105

  3. Long-Term Variability of Solar Activity

    KUSANO Kanya

      Vol. 90 ( 2 ) page: 112 - 115   2014.2

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  4. Special Topic Articles: Space Climatology 1. Preface Invited

    Kanya Kusano, Hiroki Hasegawa

    Journal of Plasma and Fusion Research   Vol. 90 ( 2 ) page: 105 - 106   2014.2

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    Language:Japanese   Publishing type:Article, review, commentary, editorial, etc. (scientific journal)  

  5. Preliminary numerical study on the cumulus-stratus transition induced by the increase of formation rate of aerosols

      Vol. 72   page: 249 - 264   2014

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    CiNii Books

    Other Link: http://hdl.handle.net/2115/55063

  6. 1. Preface(<Special Topic Article>Space Climatology)

    KUSANO Kanya, HASEGAWA Hiroki

      Vol. 90 ( 2 ) page: 105 - 106   2014

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    CiNii Books

  7. 6. Postface : Prospective in Space Climate Research(<Special Topic Article>Space Climatology)

    KUSANO Kanya

      Vol. 90 ( 2 ) page: 146 - 147   2014

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    CiNii Books

  8. Space and Earth System Modeling

    Annual report of the Earth Simulator Center     page: 103 - 107   2013.4

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    Language:English   Publisher:Earth Simulator Center, Japan Agency for Marine-Earth Science and Technology  

    CiNii Books

  9. 26aEA-12 Simulation study on the hemispheric symmetry of the solar dynamo cycle based on the flux transport dynamo model

    Shukuya Daishi, Kusano Kanya

    Meeting abstracts of the Physical Society of Japan   Vol. 68 ( 1 ) page: 257 - 257   2013.3

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    Language:Japanese   Publisher:The Physical Society of Japan (JPS)  

    CiNii Books

  10. 29aEA-1 Investigation on numerical methods for full two-fluid plasma model

    Miyoshi Takahiro, Matsumoto Yosuke, Kusano Kanya

    Meeting abstracts of the Physical Society of Japan   Vol. 68 ( 1 ) page: 297 - 297   2013.3

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    Language:Japanese   Publisher:The Physical Society of Japan (JPS)  

    CiNii Books

  11. 26pEA-2 Trigger Mechanism and Predictability of Solar Flares

    Kusano Kanya, Bamba Yumi, Yamamoto Tetsuya, Iida Yusuke, Toriumi Shin, Asai Ayumi

    Meeting abstracts of the Physical Society of Japan   Vol. 68 ( 1 ) page: 263 - 263   2013.3

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    Language:Japanese   Publisher:The Physical Society of Japan (JPS)  

    CiNii Books

  12. 26pEA-10 Numerical study of magnetic reconnection in high Raynols number plasma

    Nakabou Takashi, Kusano Kanya, Miyoshi Takahiro, Vekstein Grigory

    Meeting abstracts of the Physical Society of Japan   Vol. 68 ( 1 ) page: 265 - 265   2013.3

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    CiNii Books

  13. 小特集 俯瞰と展望:磁気リコネクション研究の最前線 2. 高速リコネクション機構の最新研究 2.5 三次元磁場構造が引き起こす爆発的現象

    草野完也, 小野 靖

    プラズマ核融合学会誌   Vol. 11   page: 780 - 783   2013

  14. 26pYC-11 Development of a modified HLLD approximate Riemann solver

    Miyoshi Takahiro, Kusano Kanya

    Meeting abstracts of the Physical Society of Japan   Vol. 67 ( 1 ) page: 276 - 276   2012.3

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    Language:Japanese   Publisher:The Physical Society of Japan (JPS)  

    CiNii Books

  15. 超水滴法の挑戦--雲微物理過程のシミュレーション (特集 雲--豊饒なる非線形科学の世界)

    島 伸一郎, 草野 完也

    科学   Vol. 80 ( 9 ) page: 929 - 933,898   2010.9

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    Language:Japanese   Publisher:岩波書店  

    CiNii Books

  16. Drift-Kinetic Modeling of Particle Acceleration and Transport in Solar Flares

    MINOSHIMA Takashi, MASUDA Satoshi, MIYOSHI Yoshizumi, KUSANO Kanya

    The astronomical herald   Vol. 103 ( 9 ) page: 552 - 560   2010.8

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    CiNii Books

  17. On the Interactive Collaboration of Observational and Experimental Studies for the Understanding of Solar Activities(<Special Review>Heavenly Bodies on the Earth)

    KUSANO Kanya, Kanya KUSANO, Solar-Terrestrial Environment Laboratory Nagoya University

    Journal of Japan Society of Fluid Mechanics   Vol. 28 ( 5 ) page: 381 - 389   2009.10

  18. Postface

    KUSANO Kanya

      Vol. 85 ( 9 ) page: 611 - 615   2009.9

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    CiNii Books

  19. 27aSA-4 Effect of Microscopic Instability on Quiet Auroral Arcs Formation

    Hasegawa H., Sugiyama T., Kageyama A., Ohno N., Hirose S., Kusano K., Sato T.

    Meeting abstracts of the Physical Society of Japan   Vol. 64 ( 1 ) page: 191 - 191   2009.3

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    Language:Japanese   Publisher:The Physical Society of Japan (JPS)  

    CiNii Books

  20. 27pSA-8 宇宙天気モデリング : コロナ質量放出の惑星間空間伝播(27pSA プラズマ宇宙物理(MHD現象:宇宙天気・モデリングと観測),領域2(プラズマ基礎・プラズマ科学・核融合プラズマ・プラズマ宇宙物理))

    片岡 龍峰, 草野 完也, 塩田 大幸, 井上 諭

    日本物理学会講演概要集   Vol. 64 ( 1 ) page: 200 - 200   2009.3

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    Language:Japanese   Publisher:一般社団法人日本物理学会  

    CiNii Books

  21. 27pSA-5 Space Weather Modeling : The Reconstruction of the Solar Active Region

    Inoue S., Shiota D., Kusano K., Kataoka R., Aasano E., Matsumoto T., Miyoshi T., Magara T., Yamamoto T., Ogino T., Shibata K.

    Meeting abstracts of the Physical Society of Japan   Vol. 64 ( 1 ) page: 199 - 199   2009.3

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    Language:Japanese   Publisher:The Physical Society of Japan (JPS)  

    CiNii Books

  22. 積雲内部における光の多重散乱過程の3次元的な解析手法

    荒木文明, 大野暢亮, 島伸一郎, 川原慎太郎, 草野完也

    計算工学講演会論文集   Vol. 14 ( 1 )   2009

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  23. Visualization of Super-Droplet Data with Physically-Based Rendering

    ARAKI Fumiaki, SHIMA Shin-ichiro, KAWAHARA Shintaro, KUSANO Kanya

      Vol. 28 ( 1 ) page: 439 - 440   2008.7

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    CiNii Books

  24. PARTICLE-BASED VISUALIZATION OF A CLOUD SIMULATED USING SUPER-DROPLET METHOD

    KAWAHARA Shintaro, ARAKI Fumiaki, SHIMA Shin-ichiro, KUSANO Kanya

    Proceedings of the conference on computational engineering and science   Vol. 13 ( 2 ) page: 869 - 872   2008.5

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  25. PHYSICALLY-BASED RENDERING OF A CLOUD ON THE CLOUD SIMULATION WITH SUPER-DROPLET METHOD

    ARAKI Fumiaki, SHIMA Shin-ichiro, KAWAHARA Shintaro, KUSANO Kanya

    Proceedings of the conference on computational engineering and science   Vol. 13 ( 2 ) page: 865 - 868   2008.5

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  26. 24aQE-4 Holistic Simulation for Quiet Auroral Arcs Formation 2

    Hasegawa H., Sugiyama T., Kageyama S., Hirose S., Kusano K., Watanabe K., Sato T.

    Meeting abstracts of the Physical Society of Japan   Vol. 63 ( 1 ) page: 227 - 227   2008.2

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  27. 24aQE-5 Data-Driven Simulation of Solar Flare Explosion and Coronal Mass Ejection

    Kusano K., Inoue S., Shiota D., Kataoka R., Asano E., Matsumoto T., Shibata K.

    Meeting abstracts of the Physical Society of Japan   Vol. 63 ( 1 ) page: 227 - 227   2008.2

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    CiNii Books

  28. Development of a next-generation MHD solver : On divergence cleaning techniques

    Miyoshi Takahiro, Kusano Kanya, Fukazawa Keiichiro, Matsumoto Yosuke, Umeda Takayuki, Sugiyama Tooru, Terada Naoki, Katoh Yuto, Nakamura Takuma, Shinohara Iku

      Vol. 2008   page: 388 - 388   2008

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    Toward peta-scale computing era, a next-generation MHD solver that is accurate and robust enough for any parameter regimes from almost incompressible turbulences to hypersonic flows should be developed. One of the key techniques for the next-generation solver must be a divergence cleaning method for the magnetic filed, which primarily affects the robustness of the multidimensional MHD solver particularly in high-resolution simulations. In this paper, several divergence cleaning methods including new methods are comparatively studied based on the HLLD Riemann solver.

    CiNii Books

  29. Study of Quiet Auroral Arc Formation with Macro-Micro Interlocked Simulations

    Hiroki Hasegawa, Tooru Sugiyama, Akira Kageyama, Shigenobu Hirose, Kanya Kusano, Kunihiko Watanabe, Tetsuya Sato

    NCTAM papers, National Congress of Theoretical and Applied Mechanics, Japan   Vol. 57   page: 214   2008

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    Language:Japanese   Publishing type:Research paper, summary (national, other academic conference)   Publisher:National Committee for IUTAM  

    The physics of quiet auroral arcs formation has been studied with Macro-Micro Interlocked (MMI) simulations. In the macro part of our simulation code, the macroscopic instability between the magnetosphere and ionosphere is described by the magneto-hydro-dynamics (MHD) model. On the other hand, in the micro part, the microscopic instability is calculated by the particle-in-cell (PIC) model. In the MHD simulation, it is shown that longitudinally striated structures of the field-aligned current are formed by an ionospheric feedback instability[1]. Further, the emission of aurora arc is obtained from the energy spectrum of accelerated electrons with the PIC simulation.
    [1] T. Sato, J. Geophys. Res., 83, 1042, 1978.

    DOI: 10.11345/japannctam.57.0.214.0

  30. Interlocked Simulations of Solar Terrestrial Environment System

    Kusano Kanya, Shiota Daikou, Inoue Satoshi, Kataoka Ryuho, Sugiyama Tooru, Asano Eiji, Matsumoto Takuma, Miyoshi Takahiro, Shima Shinichiro, Ogino Tatsuki, Shibata Kazunari

    NCTAM papers, National Congress of Theoretical and Applied Mechanics, Japan   Vol. 57 ( 0 ) page: 216 - 216   2008

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    Solar activity may impact our environment on the Earth. For instance, solar flares and coronal mass ejections (CME), which are the biggest explosion in our solar system, are believed to give a severe influence to the electromagnetic condition around the earth, so that the prediction of such space weather phenomena is required also from the view point to protect satellite systems. On the other hand, since it has been suggested even from long ago that the solar spot activity correlates with the global temperature of the earth, it is important to reveal the mechanism how solar and cosmic dynamics are related to our environment. In this study, we have tried to develop a new type of simulation model, in which several numerical models are interlocked with each other to capture complex physical processes involved in the space weather and the space climate phenomena. The current status and the future prospect of the interlocked simulation study will be reported.

    DOI: 10.11345/japannctam.57.0.216.0

  31. Interlocked MHD modeling of the Sun-Earth System for the Basic Study of Space Weather Prediction 2

    Asano Eiji, Matsumoto Takuma, Shiota Daikou, Inoue Satoshi, Kusano Kanya, Kataoka Ryuho, Ogino Tatsuki, Miyoshi Takahiro, Shibata Kazunari

      Vol. 2008   page: 383 - 383   2008

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    We have recently developed a new interlocked MHD modeling of the Sun-Earth system to understand the relationship between solar and geomagnetic storms, and to predict the associated space weather phenomena. In this study, we report our modeling results of the global solar wind structures including the propagation of a coronal mass ejection.

    CiNii Books

  32. Interlocked MHD modeling of the Sun-Earth System for the Basic Study of Space Weather Prediction 1

    Shiota Daikou, Kusano Kanya, Inoue Satoshi, Asano Eiji, Matsumoto Takuma, Kataoka Ryuho, Miyoshi Takahiro, Ogino Tatsuki, Shibata Kazunari

      Vol. 2008   page: 382 - 382   2008

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    We have recently developed a new interlocked MHD model of the Sun-Earth system, in order to understand the relationship between solar and geomagnetic storms, and to predict space weather phenomena. In this paper, we introduce the entire design of the new model, and show the preliminary results of numerical experiments for early phase of a solar storm.

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  33. 講座 高速プラズマ流と衝撃波の研究事始め 4.宇宙における高速流と衝撃波研究の最前線 4.2 太陽フレアにおける高速流とスローショック

    草野完也

    プラズマ核融合学会誌   Vol. 83 ( 4 ) page: 372 - 377   2007.4

  34. 講座 高速プラズマ流と衝撃波の研究事始め 3.高速プラズマ流を伴う計算機シミュレーションの基礎

    三好隆博, 草野完也

    プラズマ核融合学会誌   Vol. 83 ( 3 ) page: 228 - 240   2007.3

  35. 18pQC-11 Holistic Simulation for Quiet Auroral Arcs Formation

    Hasegawa H., Sugiyama T., Kageyama A., Hirose S., Kusano K., Watanabe K., Sato T.

    Meeting abstracts of the Physical Society of Japan   Vol. 62 ( 1 ) page: 189 - 189   2007.2

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  36. 超水滴法による雲形成シミュレーションの可視化

    川原慎太郎, 荒木文明, 島伸一郎, 草野完也

    数値流体力学シンポジウム講演論文集(CD-ROM)   Vol. 21st   2007

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  37. B455 超水滴法による雲 : エアロゾル相互作用の評価に向けた試み(雲物理)

    島 伸一郎, 草野 完也, 荒木 文明, 川原 慎太郎

    大会講演予講集   Vol. 91   page: 120 - 120   2007

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  38. A Carbuncle-free HLL-type Approximate Riemann Solver for HD and MHD

    Miyoshi Takahiro, Kusano Kanya

      Vol. 2007   page: 86 - 86   2007

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    A carbuncle-free multi-state Harten-Lax-van Leer (HLL)-type approximate Riemann solver for HD and MHD is newly proposed. From phenomenological consideration for numerical shock instabilities like a carbuncle phenomenon, we guess that the instabilities may appear when a numerical viscosity is insufficient for a shear wave rather than for a contact wave. In this study, the numerical viscosity for the tangential momentum is selectively added assuming the single-state tangential velocity in the Riemann fan. The new solver can be effectively embedded into the higher HLLC and HLLD Riemann solver using the usual shock-fix algorithm.

    CiNii Books

  39. Visualization of the Cloud and Rainfall Simulation with Super-droplet Method

    KAWAHARA SHINTARO, ARAKI FUMIAKI, SHIMA SHIN'ICHIRO, SUGIYAMA TOORU, KAWANO AKIO, HIROSE SHIGENOBU, KUSANO KAN'YA

    可視化情報学会誌   Vol. 26 ( Suppl.2 ) page: 27 - 28   2006.9

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    Cloud formations and precipitation are highly-complicated phenomena, and the accurate modeling of them is a crucial subject for meteorological simulations. Recently, we developed a new algorithm, which enables the first-principle simulation of cloud formation process, by introducing a new numerical concept called "super-droplet".<BR>In this paper, we report about the visualization of the cloud formation-precipitation simulation using the super-droplet method. The technique to visualize the distribution of all droplets included in a cumulus cloud will be explained, and some application results of it will be also presented for the analysis of droplet size spectrum, cloud motion, and the optical property of cloud, respectively.

    DOI: 10.3154/jvs.26.Supplement2_27

    J-GLOBAL

  40. Visualization of Multi-physics Coupled Cloud Simulation using Super-droplet Method

    ARAKI FUMIAKI, SHIMA SHIN'ICHIRO, KAWAHARA SHINTARO, KUSANO KAN'YA

    可視化情報学会誌   Vol. 26 ( Suppl.1 ) page: 87 - 90   2006.7

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    DOI: 10.3154/jvs.26.Supplement1_87

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    J-GLOBAL

  41. 30aUC-4 Hyperbolic divergence cleaning method in a uniform background flow

    Miyoshi Takahiro, Kusano Kanya

    Meeting abstracts of the Physical Society of Japan   Vol. 61 ( 1 ) page: 235 - 235   2006.3

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  42. AM06-13-009 Super Droplet Method for the Numerical Modeling of Clouds and Precipitations

    Shima Shin-ichiro, Araki Fumiaki, Kawahara Shintaro, Kusano Kanya

      Vol. 2006   page: 160 - 160   2006

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    We develop a novel cloud microphysics model, called Super Droplet Model (SDM), which enables accurate calculation for the motion, growth by condensation and evaporation, and coalescence of all the droplets in a cloud with reasonable cost in computation. We couple SDM and a non-hydrostatic cloud dynamics model and demonstrate a regional simulation of cloud formation and precipitation.

    CiNii Books

  43. AM06-19-006 MHD-PIC connection model in space plasmas

    Sugiyama Tooru, Kusano Kanya

      Vol. 2006   page: 281 - 281   2006

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    A fluid description of plasmas is useful to investigate the global structure in space plasma, such as the magnetosphere and heliosphere. It can reproduce the time evolution of macroscopic variations of density, bulk velocity and pressure. On the other hand, the microscopic dynamics of plasmas should be described by spatial and velocity distribution in the phase space. Wave-particle interaction process is the typical example for the application of the microscopic description. For these micro- and macroscopic description, different kinds of numerical approach may work well, respectively, e.g. MHD simulation for the macroscopic phenomena and PIC simulation for microscopic process. However, it is widely accepted that the cross-scale interaction between micro and macro processes plays a crucial role, for instance, in the diffusion region in the magnetic reconnection process. Therefore, a new model which can treat MHD-scale dynamics including particle kinetic effects is necessary. We have developed the new simulation method called "Interlocked simulation", in which MHD and PIC simulations are simultaneously performed. Here, we show its algorithm and some examples.

    CiNii Books

  44. AM06-19-007 Three-dimensional MHD Code for Global Simulation of the Solar Corona

    Shiota Daikou, Kusano Kanya, Miyoshi Takahiro, Nishikawa Noriaki, Shibata Kazunari

      Vol. 2006   page: 282 - 282   2006

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    We developed a new three-dimensional Magnetohydrodynamic (MHD) code for global simulation of coronal mass ejections in the solar corona. In this code, ideal MHD equations with gravity are solved by finite volume method with the monotonic upstream schemes for conservation laws (MUSCL) which achieves 3rd order spatial resolution, the HLLD nonlinear approximate Riemann solver, and the 2nd order Runge-Kutta time integration. An initial condition is built up with magneto-hydrostatic equilibrium of source surface potential field.

    CiNii Books

  45. C208 超水滴法による雲微物理過程の精密な数値シミュレーション(降水システムII)

    島 伸一郎, 草野 完也, 荒木 文明, 川原 慎太郎

    大会講演予講集   Vol. 89   page: 176 - 176   2006

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  46. Magnetic Helicity in the Solar Corona

    KUSANO Kanya

    The Astronomical herald   Vol. 99 ( 1 ) page: 7 - 17   2005.12

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  47. 25aXA-11 A nonlinear Riemann solver for ideal magnetohydrodynamics

    Miyoshi Takahiro, Kusano Kanya

    Meeting abstracts of the Physical Society of Japan   Vol. 60 ( 1 ) page: 210 - 210   2005.3

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  48. 26pXA-11 Simulation Study of the Dipole Field Reversal Mechanism in a Rotating'Spherical Shell II

    Nishikawa Noriaki, Kusano Kanya

    Meeting abstracts of the Physical Society of Japan   Vol. 60 ( 1 ) page: 233 - 233   2005.3

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  49. 25pXA-11 Mutually Exciting Three-Dimensional Reconnection in Solar Flare Onset Process

    Kusano Kanya

    Meeting abstracts of the Physical Society of Japan   Vol. 60 ( 1 ) page: 220 - 220   2005.3

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  50. AM05-08-008 Three-dimensional magnetic reconnection driven by an emerging flux tube with coronal arcade field in the Sun

    Notoya Shun, Yokoyama Takaaki, Kusano Kanya, Sakurai Takashi, Miyagoshi Takahiro, Isobe Hiroaki, Yamamoto Tetsuya

      Vol. 2005   page: 115 - 115   2005

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    We performed three-dimensional numerical simulations of the emergence of magnetic flux from the convectiove zone into the corona and its reconnection with a preexisting ambient coronal arcade field. Initially the flux tube in the convective zone is perturbed and becomes unstable to the Parker instability. The instability causes the rise and the expansion of the flux tube into the corona and the field comes into contact with the arcade field. When the upcoming field and the coronal arcade field generate current sheets between them, the reconnection occurs, causing profound changes in their connectivity. The local heating and the high-speed outflows caused by the reconnection can be seen in our simulations. We investigate how the changes in the angle of the arcade relative to the magnetic neutral line, lead to the different physical processes.

    CiNii Books

  51. 27aXH-8 2-dimensional simulation for dust plasma particles in shear flow

    Takaishi Takeshi, Kusano Kanya

    Meeting abstracts of the Physical Society of Japan   Vol. 59 ( 1 ) page: 212 - 212   2004.3

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  52. Magnetic Helicity Injection Into the Magnetospheric System

    Miyoshi T., Kusano K.

    Meeting abstracts of the Physical Society of Japan   Vol. 58 ( 1 ) page: 210 - 210   2003.3

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  53. Relation between magnetic helicity injection and flare activities in active region NOAA 8100

    T Yokoyama, K Kusano, T Maeshiro, T Sakurai

    MAGNETIC HELICITY AT THE SUN, IN SOLAR WIND AND MAGNETOSPHERES: VISTAS FROM X-RAY OBSERVATORIES   Vol. 32 ( 10 ) page: 1949 - 1952   2003

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    The analysis of the magnetic helicity injection into active region NOAA 8100 is shown. This region is known as a source of many coronal activities such as flares. It is found that most of the flare events occurred about half a day after the helicity injection rate changed its sign. And the positions of Ha emission in flares well correspond to the helicity inversion lines in space. These results suggest that the sign-reversal of the helicity injection rate is a key signature of flare activities. (C) 2003 COSPAR. Published by Elsevier Ltd. All rights reserved.

    DOI: 10.1016/S0273-1177(03)00773-7

    Web of Science

  54. Prospect for Multiple Time and Spatial Scale Simulation Research in Astrophysical Plasma Phenomena, Multiple Scale Simulation of Magnetic Reconnection Phenomena in the Solar Corona

    KUSANO Kanya

    Journal of Plasma and Fusion Research   Vol. 79 ( 5 ) page: 496 - 503   2003

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    Although magnetic reconnection is believed to be a key process in solar flares, the flares' triggering mechanism remains a long-standing problem. In order to resolve this issue, the physical linkage between the magnetohydrodynamic (MHD) process in the macroscopic scale and the plasma kinetics in the microscopic scale has to be understood. Multiple-scale simulation, which can precisely describe the nonlinear process of the MHD equations as well as the complexity in the solar corona, will play a crucial role in this field of study.

    DOI: 10.1585/jspf.79.496

    CiNii Books

    Other Link: https://jlc.jst.go.jp/DN/JALC/00229591198?from=CiNii

  55. Measurement of magnetic helicity flux into the solar corona

    K Kusano, T Maeshiro, T Yokoyama, T Sakurai

    MAGNETIC HELICITY AT THE SUN, IN SOLAR WIND AND MAGNETOSPHERES: VISTAS FROM X-RAY OBSERVATORIES   Vol. 32 ( 10 ) page: 1917 - 1922   2003

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    We developed a new methodology which can determine magnetic helicity flux across the photosphere based on the magnetograph observation. In order to derive the helicity flux, first the velocity tangential to the solar surface is constructed by applying a correlation tracking technique on the magnetic observation, and secondly the velocity component across the photosphere is derived from the condition that the magnetic evolution must be consistent with the induction equation. Through this procedure, we can determine the helicity flow across the photosphere as a function of time and space. Based on this new method, we analyzed magnetic helicity of the active regions NOAA 906 and 9077, using the data taken by SOHO/MDI and the vector magnetograph at NAOJ/Tokyo. As a result, it was revealed that positive and negative helicity is supplied in each region simultaneously. In particular, temporary activation of the helicity injection of the both signs was observed prior to X-class flare events in the GOES classification. The investigation on the helicity distribution suggests some relationship between flare onset and the increase of complexity in the helicity structure. (C) 2003 COSPAR. Published by Elsevier Ltd. All rights reserved.

    DOI: 10.1016/S0273-1177(03)00772-5

    Web of Science

  56. Annihilation of magnetic helicity: A new model for solar flare onset

    K Kusano, T Yokoyama, T Maeshiro, T Sakurai

    MAGNETIC HELICITY AT THE SUN, IN SOLAR WIND AND MAGNETOSPHERES: VISTAS FROM X-RAY OBSERVATORIES   Vol. 32 ( 10 ) page: 1931 - 1936   2003

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    Although magnetic reconnection is believed to be a key process for solar flares, the onset mechanism of flares remains as a long-standing problem. In this paper, we propose a new model for solar flares, in which magnetic reconnection converts oppositely-sheared field into the shear-free field. This process can be understood as the annihilation of magnetic helicities with, different signs, and it is consistent with the recent results of the helicity observations. Numerical simulations were carried, which show that, if the helicity is sharply, reversed within a magnetic arcade, reconnection quickly grows in the helicity inversion layer, driving explosive dynamics. The explosive process appears as a result of nonlinear instability, which grows faster than exponentially with time. Based on the results, we predict that the coexistence of the positive and negative helicity is crucial for the onset of flares. (C) 2003 COSPAR. Published by Elsevier Ltd. All rights reserved.

    DOI: 10.1016/S0273-1177(03)00765-8

    Web of Science

  57. MHD Phenomena in Astronomical and Space Plasmas

    KUSANO Kanya

    Journal of plasma and fusion research   Vol. 77 ( 7 ) page: 691 - 697   2001.7

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    Magnetohydrodynamics (MHD) provide a very important model for our understanding of the structure and evolution of space and astronomical plasmas, such as the Sun, solar corona, and planetary magnetosphere. This paper outlines two key concepts, reconnection and dynamo, those play an essential role in the energetic activity of a variety of astronomical and space plasmas.

    CiNii Books

    Other Link: http://dl.ndl.go.jp/info:ndljp/pid/10454465

  58. The Useful Model Called MHD 6. MHD in Astronomical Plasmas

    Journal of Plasma and Fusion Research   Vol. 77 ( 7 ) page: 691   2001

  59. Spontaneous Variation in a Rotating Magnetosphere

    J. Plasma Fusion Res. Series   Vol. 4   page: 536 - 539   2001

  60. INTERNATIONAL ASTRONOMICAL UNION SYMPOSIUM 203, Recent Insights into the Physics of the Sun and Heliosphere, Highlights from SOHO and Other Space Missions

    The Astronomical Society of the Pacific     page: 195 - 198   2001

  61. 26pYN-8 Magnetic Helicity Transport in Three Dimensional Magnetic Arcades

    Kusano Kanya

    Meeting abstracts of the Physical Society of Japan   Vol. 54 ( 2 ) page: 179 - 179   1999.9

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  62. Stability Analysis of Wave Propagation in 2-Fluid Dusty Plasma System

    J. Plasma Fusion Res. Series   Vol. 2   page: 177 - 179   1999

  63. Magnetic Helicity in Space and Laboratory Plasmas, Geophysical Monograph 111

    the American Geophysical Union     page: 149 - 156   1999

  64. Solar Flare,Catastrophe in High Temperature Plasma

    KUSANO Kanya

    Meeting abstracts of the Physical Society of Japan   Vol. 53 ( 2 ) page: 948 - 948   1998.9

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  65. Introduction to Plasma Computer Simulation V 6. Introduction to MHD Simulation

    Journal of Plasma and Fusion Research   Vol. 74 ( 9 ) page: 1030   1998

  66. Physics of Solar Flares

    Kusano Kanya, Tsuneta Saku

    Butsuri   Vol. 53 ( 9 ) page: 656 - 662   1998

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    DOI: 10.11316/butsuri1946.53.656

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    Other Link: https://jlc.jst.go.jp/DN/JALC/00056151794?from=CiNii

  67. Physics of Dusty Plasmas: Seventh Workshop

    The Americal Institute of Physics     page: 111 - 115   1998

  68. Observational Plasma Astrophysics: Five Years of Yohkoh and Beyond

    Kluwer Acadamic Publichers     page: 185 - 186   1998

  69. Observational Plasma Astrophysics: Five Years of Yohkoh and Beyond

    Kluwer Acadamic Publichers     page: 331 - 332   1998

  70. Nonlinear magnetohydrodynamics in solar flares

    K Kusano, K Nishikawa, Y Suzuki

    JOURNAL OF THE KOREAN PHYSICAL SOCIETY   Vol. 31   page: S210 - S213   1997.8

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    The nonlinear magnetohydrodynamics (MHD) in solar flares is considered using two dimensional numerical simulations. The results are analyzed based on the bifurcation theory of the linear force-free field [K. Kusano, et al., Astrophys. J. 441 942 (1995)]. The simulation results show that a transition from a loop type configuration into an island type configuration indeed takes place as the bifurcation theory predicted. The dependence of the transition dynamics on the resistivity is considered in detail.

    Web of Science

  71. Nonlinear magnetohydrodynamics in solar flares

    K Kusano, K Nishikawa, Y Suzuki

    JOURNAL OF THE KOREAN PHYSICAL SOCIETY   Vol. 31   page: S210 - S213   1997.8

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    The nonlinear magnetohydrodynamics (MHD) in solar flares is considered using two dimensional numerical simulations. The results are analyzed based on the bifurcation theory of the linear force-free field [K. Kusano, et al., Astrophys. J. 441 942 (1995)]. The simulation results show that a transition from a loop type configuration into an island type configuration indeed takes place as the bifurcation theory predicted. The dependence of the transition dynamics on the resistivity is considered in detail.

    Web of Science

  72. MHD Simulation of a Rapidly Rotating Magnetosphere

    MIYOSHI Takahiro, KUSANO Kanya

      Vol. 16   page: 379 - 380   1997.7

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  73. MHD Energy Relaxation Mechanism in Solar Corona

    KUSANO Kanya

      Vol. 16   page: 377 - 378   1997.7

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  74. Three-dimensional simulation study of the magnetohydrodynamic relaxation process in the solar corona .2.

    Y Suzuki, K Kusano, K Nishikawa

    ASTROPHYSICAL JOURNAL   Vol. 474 ( 2 ) page: 782 - &   1997.1

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    Three-dimensional dynamics of solar coronal magnetic loops, which is caused by the photospheric twisting motion, is investigated in detail by using magnetohydrodynamic numerical simulations. It is found that, as a result of the rising of the magnetic loops, isolated flux tubes (plasmoids) are generated on top of the loops through magnetic reconnection. During the reconnection process, the magnetic energy of the mode coupled with the potential held is partially converted into the mode decoupled from it. We also analyze the linear stability of the coupled mode and reveal that it is destabilized when the loop height and the magnetic helicity exceed the critical values predicted from the bifurcation theory. Furthermore, we reveal that three-dimensional mode couplings have the effect of concentrating the helicity into an unstable mode, as well as the effect of reducing the growth rate of the instability.

    Web of Science

  75. Three-Dimensional Magnetohydrodynamic Simulation of a Rapidly Rotating Magnetosphere

    Miyoshi Takahiro, Kusano Kanya, Nishikawa Kyoji

    Abstracts of the meeting of the Physical Society of Japan. Sectional meeting   Vol. 1996 ( 4 ) page: 168 - 168   1996.9

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  76. Magnetic Buoyancy Instabilities in the Sheared Magnetic Field

    Moriyama Katsushi, Kusano Kanya, Nishikawa Kyoji

    Abstracts of the meeting of the Physical Society of Japan. Sectional meeting   Vol. 1996 ( 4 ) page: 167 - 167   1996.9

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  77. Bifurcation and stability of coronal magnetic arcades in a linear force-free field

    K Kusano, K Nishikawa

    ASTROPHYSICAL JOURNAL   Vol. 461 ( 1 ) page: 415 - 423   1996.4

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    The bifurcation structure as well as the stability property of the solar coronal magnetic arcades in a linear force-free field (LFFF) is carefully investigated. It is clarified that two different modes can cause the bifurcation of the minimum energy arcade profile: the symmetric mode (SM), which has a zero wavevector, and the undulating mode (UM), which has a nonzero wavevector parallel to the magnetic neutral lines. Depending on the geometry and the magnetic helicity contained in the arcades, the minimum energy state is switched among three different solutions of the LFFF: the coupled solution (CS), which consists only of the components coupled with the potential held; the mixed solution (MS), which is composed of the CS and the SM; and the MS of the CS and the UM. It is found that, once the LFFF bifurcates into the CS and the MS, the CS is always unstable against the SM or the UM. Based on the discussion about the relationship between the excess energy and the growth rate, it is proposed that the preflare state is a nonlinearly growing stage of these instabilities rather than a metastable state.

    Web of Science

  78. Computer simulations of pulsed-laser induced coherent plasma oscillations in GaAs crystals

    T Ueda, K Kusano, M Sasaki, M Inoue

    JOURNAL OF THE PHYSICAL SOCIETY OF JAPAN   Vol. 65 ( 3 ) page: 803 - 810   1996.3

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    Language:English   Publisher:PHYSICAL SOC JAPAN  

    One-dimensional transport equations for pulsed-laser induced space-charge distributions in GaAs crystals have been computed using a finite difference procedure by two models; (a) Model A for i-GaAs with an applied dc electric field under a uniform illumination over the crystal and (b) Model B for n- and i-GaAs without the electric field under a half illumination to simulate the ''transient thermoelectric effect'' (TTE). With Model A, the temporal and spatial evolutions of restored space-charge density of photoexcited electrons and holes are obtained, from which an induced electric field is found to oscillate with a single frequency of plasma oscillations (0.3-2THz), in satisfactory agreement with reported experiments. Model B calculations have revealed that near the boundary between the illuminated and non-illuminated regions, the appreciable enhancement of space-charge densities and induced electric fields are observed, which diffuse or drift toward a positive x direction, showing characteristic damping oscillations with two frequency components f(0) due to the doped donor electrons and f(1) due to the doped and photoexcited electrons of plasma oscillations. Furthermore, the induced TTE voltages measured across both ends of the crystal without dc electric field are simulated to show similar coherent plasma oscillations.

    DOI: 10.1143/JPSJ.65.803

    Web of Science

  79. Astronomical Society of the Pacific Conference Series, Astronomical Society of the Pacific Conference Series Volume 111

    Astronomical Society of the Pacific     page: 375 - 378   1996

  80. Research on Simnlation Sciences in INSAM

    Journal of Plasma and Fusion Research   Vol. 72 ( 8 ) page: 750   1996

  81. Magnetodynamic Phenomena in the Solar Atmosphere, Prototypes of Stellar Magnetic Activity

    Kluwer Academic Publishers     page: 303 - 304   1996

  82. Astronomical Society of the Pacific Conference Series, Astronomical Society of the Pacific Conference Series Volume 111

    Astronomical Society of the Pacific     page: 280 - 285   1996

  83. Three dimensional simulation study of the magntohydrodynamic relaxation process in the solar corona

    Proc. the IAU Colloquium No. 153 Magnetodynamic Phenomena in the Solar Atmosphere Kluwer Academic     page: 587   1995

  84. Proc. in Fourth International Toki Conference on Plasma Physics and Controlled Nuclean Fusion

    European Space Agency Publications Division     page: 253 - 254   1993

  85. Proc. in Fourth International Toki Conference on Plasma Physics and Controlled Nuclean Fusion

    European Space Agency Publications Division     page: 219 - 221   1993

  86. 25a-G-12 Convection in Earth's Outer Core and Dynamo

    Kusano Kanya

      Vol. 1992 ( 4 ) page: 73 - 73   1992.9

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    Language:Japanese   Publisher:The Physical Society of Japan (JPS)  

    CiNii Books

  87. SIMULATION STUDY ON DOUBLE RECONNECTION IN THE ULTRA-LOW-Q CONFIGURATION

    K SUZUKI, Z YOSHIDA, K KUSANO

    NUCLEAR FUSION   Vol. 31 ( 1 ) page: 179 - 183   1991.1

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    Language:English   Publishing type:Rapid communication, short report, research note, etc. (scientific journal)   Publisher:INT ATOMIC ENERGY AGENCY  

    Double tearing modes in ultra-low-q equilibria have been simulated by three-dimensional MHD calculations. Spatially localized MHD relaxation is shown to be driven by double tearing modes, which bring the field configuration in the unstable region to a Taylor-like relaxed state. When the pitch minimum of the initial state is located near the centre of the plasma, the central value of q decreases rapidly and the outer magnetic island replaces the original magnetic axis. When the pitch minimum is located near the wall, the central core region remains stable and reconnection occurs in a limited intermediate region.

    DOI: 10.1088/0029-5515/31/1/017

    Web of Science

  88. Simulation study of the non-linear dynamics in a reversed-field pinch configuration

    Nucl. Fusion Suppl.   Vol. 2   page: 181 - 190   1991

  89. SIMULATION STUDY OF THE SELF-SUSTAINMENT MECHANISM IN THE REVERSED-FIELD PINCH CONFIGURATION

    K KUSANO, T SATO

    NUCLEAR FUSION   Vol. 30 ( 10 ) page: 2075 - 2096   1990.10

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    Language:English   Publisher:INT ATOMIC ENERGY AGENCY  

    DOI: 10.1088/0029-5515/30/10/009

    Web of Science

  90. 31a-TE-10 Self-Sustainment Mechanism of the Reversed-Field Pinch Configuration

    KUSANO Kanya

      Vol. 44 ( 4 ) page: 210 - 210   1989.3

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    Language:Japanese   Publisher:The Physical Society of Japan (JPS)  

    CiNii Books

  91. Theory of Fusion Plasma, Proc.\ Joint Varenna-Lausanne International Workshop, (EUR 12149-EN)

    Editrice Compositori     page: 217 - 224   1989

  92. <RESEARCH REPORT>A Simulation of Driven Reconnection by a High Precision MHD Code

    Kusano Kanya, Ouchi Yasuo, Hayashi Takaya, Horiuchi Ritoku, Watanabe Kunihiko, Sato Tetsuya

    Research report   Vol. 863   page: 34 - 46   1988.3

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    Language:English   Publisher:National Institute for Fusion Science  

    CiNii Books

  93. Global and Local Magneto hydrodynamic Relarations(共著)

    Physics of Mirrors, Reversed Field Pinches and Compact Tori   Vol. 1   page: 397   1988

  94. Physics of Mirrors, Reversed Field Pinches and Compact Tori. Proceedings of the Course and Workshop (EUR-11335-EN)

    Editrice Compositori     page: 397 - 409   1988

  95. SIMULATION STUDY OF RELAXATION PROCESS IN THE FINITE-BETA REVERSED-FIELD PINCH

    K KUSANO

    JOURNAL OF THE PHYSICAL SOCIETY OF JAPAN   Vol. 56 ( 3 ) page: 963 - 972   1987.3

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    Language:English   Publisher:PHYSICAL SOCIETY JAPAN  

    DOI: 10.1143/JPSJ.56.963

    Web of Science

  96. 1987 International Conference on Plasma Physics, Proc. of the Invited Papers (Kiev, USSR April 6-12, 1987)

    World Scientific     page: 1116 - 1146   1987

  97. Experimental Studies of Reversed Field Pinch REPUTE (]G0001[) and Ultra-Low-q■.-. Discharge(共著)

    Plasma Physics and Controlled Nuclear Fusion Research 1986   Vol. 2   page: 433   1987

  98. Three-Dimensional MHD Studies of the Magnetic Energy Relaxation Processes(共著)

    Plasma Physics and Controlled Nuclear Fusion Research 1986   Vol. 2   page: 693   1987

  99. Three-dimensional MHD studies of the magnetic energy relaxation processes

    Nucl. Fusion Suppl.   Vol. 2   page: 693 - 700   1987

  100. Spontaneous formation of magnetohydrodynamic equilibrium profiles: tokamak, reversed-field pinch, and their intermediates

    Phys. Fluids   Vol. 30 ( 8 ) page: 2465 - 2469   1987

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  101. Spontaneous Formation of Magnetohydrodynamic Equilibrium Profiles : toRamaR, reversed-field pinch, and their intermediates(共著)

    Phys. Fluids   Vol. 30 ( 8 ) page: 2465 - 2469   1987

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  102. Simulation Study of Relaxation Process in the Finite β Reversed-Field Pinch

    Kanya Kusano

    Journal of the Physical Society of Japan   Vol. 56 ( 3 ) page: 963 - 972   1987

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    Language:English  

    By means of 3D magnetohydrodynamic simulations, the relaxation process in the finite β reversed-field pinch (RFP) is investigated. It is confirmed that the nonlinear reconnection process is the dominant mechanism of the RFP relaxation even in the system of finite β. The nonlinear reconnection rate is almost halved compared with that in the zero β case. The relaxed state of finite β is dynamically achieved. This state has a flat pressure profile and is well approximated by the Bessel-function model in the central region. The simulation result agrees with the partially relaxed state model. The β-limit is estimated based on the Suydam criterion, and consequently, it is found that the stable area on the F-θ diagram is narrowed as the heat loss decreases. © 1987, THE PHYSICAL SOCIETY OF JAPAN. All rights reserved.

    DOI: 10.1143/JPSJ.56.963

    Scopus

  103. Non-linear coupling effects on the relaxation process in the reversed field pinch

    K. Kusano, T. Sato

    Nuclear Fusion   Vol. 27 ( 5 ) page: 821 - 832   1987

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    Language:English   Publishing type:Book review, literature introduction, etc.  

    The relaxation process in the reversed field pinch has been studied extensively with three-dimensional magnetohydrodynamic simulations. It is found that the non-linear coupling between multiple helicity modes plays a leading role in the relaxation process. Specifically, the (m
    n)=(0
    1) island is excited as a result of non-linear coupling between the linearly unstable m=l modes, with a toroidal mode number difference of one. The m=0 island is then subject to axisymmetric non-linear reconnection whereby reversed flux is effectively generated in the outer region. It should be noted that although the axisymmetric non-linear reconnection of m=0 island is the dominant relaxation process, helical non-linear reconnection of linearly unstable m=l modes also plays some role in the relaxation of the whole system. It is also found that through this multiple helicity relaxation process, Taylor's minimum energy state is realized. The simulation results are generally consistent with experimental observations in the sustainment phase. This indicates that the multiple helicity relaxation process is of fundamental importance in the maintenance of the reversed field during the sustainment phase as well as in the self-reversal during the set-up phase. The relation between relaxation and aspect ratio has also been examined and it is found that the relaxation process is not strongly affected by the aspect ratio. © IOP Publishing Ltd.

    DOI: 10.1088/0029-5515/27/5/011

    Scopus

  104. Experimental studies of reversed field pinch REPUTE-1 and ultra-low-q discharge

    Nucl. Fusion Suppl.   Vol. 2   page: 433 - 440   1987

  105. SIMULATION STUDY OF THE SELF-REVERSAL PROCESS IN THE REVERSED-FIELD PINCH BASED ON A NONLINEARLY DRIVEN RECONNECTION MODEL

    K KUSANO, T SATO

    NUCLEAR FUSION   Vol. 26 ( 8 ) page: 1051 - 1061   1986.8

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    Language:English   Publisher:INT ATOMIC ENERGY AGENCY  

    DOI: 10.1088/0029-5515/26/8/005

    Web of Science

  106. 1p-BB-2 トロイダル電流系のMHD緩和現象(プラズマ物理・核融合(RFP))

    吉田 善章, 山田 弘司, 井上 信幸, 草野 完也, 佐藤 哲也, 村上 好樹

    年会講演予稿集   Vol. 41 ( 4 ) page: 260 - 260   1986.3

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    Language:Japanese   Publisher:一般社団法人日本物理学会  

    CiNii Books

  107. 1p-BB-3 トロイダル電流系のMHD緩和現象II(プラズマ物理・核融合(RFP))

    山田 弘司, 村上 好樹, 吉田 善章, 井上 信幸, 草野 完也, 佐藤 哲也

    年会講演予稿集   Vol. 41 ( 4 ) page: 260 - 260   1986.3

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    Language:Japanese   Publisher:一般社団法人日本物理学会  

    CiNii Books

  108. 3D MHD Studies of Dynamic Processes in the Reversed- Field Pinch(共著)

    Plasma Physics and Controlled Nuclear Fusion Research 1984   Vol. 2   1985

  109. 3D MHD studies of dynamic processes in the reversed-field pinch

    Nucl. Fusion Suppl.   Vol. 2   page: 461 - 465   1985

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KAKENHI (Grants-in-Aid for Scientific Research) 49

  1. Understanding and realization of advanced prediction for solar explosions with the integrated model including from stellar convection zone to interplanetary space

    Grant number:21H04492  2021.4 - 2026.3

    Grants-in-Aid for Scientific Research  Grant-in-Aid for Scientific Research (A)

      More details

    Authorship:Principal investigator 

    Grant amount:\35100000 ( Direct Cost: \27000000 、 Indirect Cost:\8100000 )

  2. Theoretical studies on evolution of stellar coronae

    Grant number:21H01124  2021.4 - 2024.3

    Grants-in-Aid for Scientific Research  Grant-in-Aid for Scientific Research (B)

      More details

    Authorship:Coinvestigator(s) 

  3. Steering Committee of Project for Solar-Terrestrial Environment Prediction

    Grant number:20H05604  2020.4 - 2021.3

    Grants-in-Aid for Scientific Research  Grant-in-Aid for Scientific Research on Innovative Areas (Research in a proposed research area)

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    Authorship:Principal investigator 

    Grant amount:\3900000 ( Direct Cost: \3000000 、 Indirect Cost:\900000 )

  4. 宇宙の構造形成と進化から惑星表層環境変動までの統一的描像の構築

    2020 - 2022

    「富岳」成果創出加速プログラム  サブ課題D「太陽活動と惑星環境変動の解明」

  5. 萌芽的課題「太陽系外惑星(第二の地球)の誕生と太陽系内惑星環境変動の解明」

    2017 - 2019

    ポスト「京」で重点的に取り組むべき社会的・科学的課題に関するアプリケーション開発・研究開発  サブ課題C「太陽活動による地球環境変動の解明」

  6. Statistical Study for Understanding and Prediction of Solar Explosive and Eruptive Phenomena

    Grant number:16H07478  2016.8 - 2018.3

    Japan Society for the Promotion of Science  Grants-in-Aid for Scientific Research Grant-in-Aid for Research Activity start-up  Grant-in-Aid for Research Activity start-up

    Bamba Yumi, KUSANO Kanya, INOUE Satoshi, IMADA Shinsuke, SHIOTA Daikou, Lee Kyoung-Sun, Leka K. D., Brooks David H., KUSANO Kanya, INOUE Satoshi, IMADA Shinsuke, SHIOTA Daikou, Lee Kyoung-Sun, Leka K. D., Brooks David H.

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    Authorship:Other 

    We aim to decide parameters for prediction of solar explosive and eruptive events based on understanding of physical processes. We performed observational verification of theoretical models and statistical data analysis for solar flares observed by the Hinode and SDO satellites. We quantitatively confirmed the physical processes and occurrence conditions of solar flare. Moreover, we proposed new candidates of parameters that would be useful for flare prediction, and discussed universality of our flare trigger model and its parameters.

  7. Development of International Collaboration for Solar-Terrestrial Environment Prediction

    Grant number:15K21709  2015.11 - 2020.3

    Grants-in-Aid for Scientific Research  Grant-in-Aid for Scientific Research on Innovative Areas (Research in a proposed research area)

    Kusano Kanya

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    Authorship:Principal investigator 

    Grant amount:\64610000 ( Direct Cost: \49700000 、 Indirect Cost:\14910000 )

    研究成果の概要(英文):Project for Solar-Terrestrial Environment Projection developed cross-disciplinary research to explore changes in the solar-terrestrial environment by integrating the latest observation systems and advanced physical models, and synergistically develops scientific research and the operation of space weather prediction. In this research, we developed international joint research for that purpose in various ways. Through that, we made many scientific results about, for instance, the international comparison of solar flare prediction, the development of radio propagation simulator based on ionospheric fluctuation prediction, the international joint solar observation with China, the US-Japan joint analysis of satellite data of the magnetospheric waves, the reproduction of the past solar-terrestrial environment based on ancient literature in Europe and Japan.

  8. Solar-Terrestrial Environment Prediction as Science and Social Infrastructure

    Grant number:2708  2015.6 - 2020.3

    Japan Society for the Promotion of Science  Grants-in-Aid for Scientific Research Grant-in-Aid for Scientific Research on Innovative Areas (Research in a proposed research area)  Grant-in-Aid for Scientific Research on Innovative Areas (Research in a proposed research area)

      More details

    Authorship:Principal investigator 

  9. Steering Committee of Project for Solar-Terrestrial Environment Prediction

    Grant number:15H05812  2015.6 - 2020.3

    Grant-in-Aid for Scientific Research on Innovative Areas (Research in a proposed research area)

    Kusano Kanya

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    Authorship:Principal investigator 

    Grant amount:\66300000 ( Direct Cost: \51000000 、 Indirect Cost:\15300000 )

    Project for Solar-Terrestrial Environment Projection developed cross-disciplinary research to explore changes in the solar-terrestrial environment by integrating the latest observation systems and advanced physical models, and synergistically develops scientific research and the operation of space weather prediction. We have conducted research that contributes to the development of space weather forecasts and the formation of a social infrastructure that can cope with severe space weather disasters. Therefore, to maximize research results through organic collaboration across the various field, the Steering Committee works to implement appropriate research strategies, earnest self-evaluation, strengthen collaboration with academia, industry, and international partners. We worked also for the development of young researchers, active press releases and outreach activities through WEB, Newsletters, public lectures, lectures in schools, scientific magazines, and scientific TV programs.

  10. Understanding and prediction of the solar storm

    Grant number:15H05814  2015.6 - 2020.3

    Japan Society for the Promotion of Science  Grants-in-Aid for Scientific Research Grant-in-Aid for Scientific Research on Innovative Areas (Research in a proposed research area)  Grant-in-Aid for Scientific Research on Innovative Areas (Research in a proposed research area)

    Ichimoto Kiyoshi

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    Authorship:Coinvestigator(s) 

    This project aimed to improve our capability for predicting the solar-terrestrial environment by understanding the mechanism of solar explosions and the propagation of the consequent disturbances to the Earth using physics-based models. As a result, we developed a reliable scheme for predicting the occurrence of large-scale solar explosions by identifying its trigger mechanism using high-precision measurements of the magnetic fields on the Sun and advanced modeling based on physical principles. Also we developed a methodology for forecasting solar storms that reach the Earth at the occurrence of the solar explosion by combining optical and radio observations and advanced modeling of the solar wind and CME. Some of our achievements are utilized in real operation in the space weather forecast center of the National Institute of Information and Communication Technology.

  11. Solar-Terrestrial Environment Prediction as Science and Social Infrastructure

    2015.4 - 2020.3

    Grant-in-Aid for Scientific Research 

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    Authorship:Principal investigator 

  12. Galactic cosmic rays, heliospheric environment, and the terrestrial climate for the past 40,000 years

    Grant number:25287051  2013.4 - 2018.3

    Japan Society for the Promotion of Science  Grants-in-Aid for Scientific Research Grant-in-Aid for Scientific Research (B)  Grant-in-Aid for Scientific Research (B)

    Miyahara Hiroko, YOKOYAMA Yusuke, TOKANAI Fuyuki, YOKOYAMA Yusuke, TOKANAI Fuyuki

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    Authorship:Coinvestigator(s) 

    In this study, we analyzed the cosmogenic nuclides in tree rings and ice cores to investigate the periodic variations of solar activity and the galactic cosmic rays in the past. Based on the time profile, we also examined the long-term variations of large-scale structure of heliospheric magnetic field. In addition, we conducted measurements of oxygen isotopes in tree rings to understand the solar influence on climate. As a result, it turned out that solar activity plays important role in the variations of precipitation in addition to the temperatures. We also examined the possible solar influence on meteorological phenomena focusing on the solar rotational period. As a result, it was suggested that solar activity shows a significant impact even at a meteorological time scale.

  13. Study of the dynamics and anisotropy of flow structures in turbulence by large scale numerical analysis

    Grant number:25247014  2013.4 - 2018.3

    Japan Society for the Promotion of Science  Grants-in-Aid for Scientific Research Grant-in-Aid for Scientific Research (A)  Grant-in-Aid for Scientific Research (A)

    Kimura Yoshifumi, KANEDA Yukio, YOSHIMATSU Katsunoni, SAKAJO Takashi, MATSUO Takayasu, KANEDA Yukio, YOSHIMATSU Katsunoni, SAKAJO Takashi, MATSUO Takayasu

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    Authorship:Coinvestigator(s) 

    The objective of this research project was to study the dynamics and singularity of flow structures such as vortices and waves in turbulence using a large scale computer simulations. We placed astrophysical- and geophysical turbulence as the main research target because the anisotropy of flow structures plays the essential role in them. As the major achievements of the project, we can raise (1) clarification of the mechanism of development of the energy spectrum for stably stratified turbulence, and (2) understanding of singularity and characteristic geometrical features in the vortex reconnection process. In particular, it is realized that the second result is largely related to the problem of regularity of the Navier-Stokes equations, one of the seven millennium problems by the Clay Mathematical Institute.

  14. The study of solar flare triggering mechanism and its prediction

    Grant number:23340045  2011.4 - 2016.3

    Japan Society for the Promotion of Science  Grants-in-Aid for Scientific Research Grant-in-Aid for Scientific Research (B)  Grant-in-Aid for Scientific Research (B)

    Kusano Kanya, ASAI Ayumi, IMADA Shinsuke, SHIOTA Daiko, MIYOSHI Takahiro, MINOSHIMA Takashi, ASAI Ayumi, IMADA Shinsuke, SHIOTA Daiko, MIYOSHI Takahiro, MINOSHIMA Takashi

      More details

    Authorship:Principal investigator 

    Grant amount:\17420000 ( Direct Cost: \13400000 、 Indirect Cost:\4020000 )

    We studied the triggering mechanism of solar flares by systematically surveying the nonlinear dynamics caused by a wide variety of magnetic structures in terms of three-dimensional magnetohydrodynamic simulations and the analyses of data observed by solar physics satellites Hinode and SDO. As a result, we determined that two different types of small magnetic structures favor the onset of solar eruptions. These structures, which should appear near the magnetic polarity inversion line (PIL), include magnetic fluxes reversed to the potential component or the nonpotential component of major field on the PIL.
    These results suggest that forecasting of solar eruptions is possible with sophisticated observation of a solar magnetic field, although the lead time must be limited by the timescale of changes in the small magnetic structures.

  15. 太陽フレア・トリガ機構の解明とその発生予測

    2011.4 - 2015.3

    科学研究費補助金  基盤研究(B)

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    Authorship:Principal investigator 

  16. Laboratory experiment for verification of cosmic-ray influence on cloud formation and global climate

    Grant number:23654166  2011 - 2012

    Japan Society for the Promotion of Science  Grants-in-Aid for Scientific Research Grant-in-Aid for Challenging Exploratory Research  Grant-in-Aid for Challenging Exploratory Research

    MASUDA Kimiaki, IZAWA Yuki, SUZUKI Asami, TAKEUCHI Yuya, ITOW Yoshitaka, SAKO Takashi, MATSUMI Yutaka, NAKAYAMA Tomoki, UEDA Sayako, KUSANO Kanya, MIURA Kazuhiko

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    In order to verify a hypothesis that atmospheric ions produced by ionization of cosmic-rays promote formation and growth of aerosol particles and control the earth's climate, we conducted a preliminary study on laboratory experiments. A system has been constructed for introduction of syntesis air with minor constituents to a reaction chamber and measurement of reaction products after irradiation of UV lights and ionizing radiation. We irradiated beta-rays or heavy ion beam and measured ion density, aerosol particle density and particle size distribution. As a result, we obtained data showing a linear relation between ion density and aersol particle density , saturation tendensy at high ion density, time variation of particle size distribution, etc. With these results, more detailed experiments will be ready.

  17. 連結階層シミュレーションで探るマルチフィジックス・プラズマダイナミクス

    2007.4 - 2010.3

    科学研究費補助金  基盤研究(B)

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    Authorship:Principal investigator 

  18. Research on multi-scale physics of ITER plasmas by using integrated transport code

    Grant number:19360415  2007 - 2010

    Japan Society for the Promotion of Science  Grants-in-Aid for Scientific Research Grant-in-Aid for Scientific Research (B)  Grant-in-Aid for Scientific Research (B)

    YAGI Masatoshi, FUKUYAMA Atsushi, TAKIZUKA Tomonori, SHIMIZU Katsuhiro, TOKUDA Shinji, TOMITA Yukihiro, KAGEYAMA Akira, KUSANO Kanya, SUZUKI Yoshio, NAITOU Hirohi, HATAYAMA AKIYOSHI, OOSAWA KAZUHITO, FUKUYAMA Atsushi, TAKIZUKA Tomonori, SHIMIZU Katsuhiro, TOKUDA Shinji, TOMITA Yukihiro, KAGEYAMA Akira, KUSANO Kanya, SUZUKI Yoshio, NAITOU Hirohi, HATAYAMA AKIYOSHI, OOSAWA KAZUHITO

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    Authorship:Coinvestigator(s) 

    The interface between plasma core transport code TASK/TOPICS and edge divertor code SONIC has been developed, which enables the self-consistent integrated transport simulation for whole plasma. Using this code, the heat flux into diverter plate has been evaluated in the self-consistent manner. The results were reported in 23rd IAEA Fusion Energy Conference 2010. In addition, the multi-scale, multi-physics simulation study on fusion plasma has been performed. It is found that non-local effect due to the nonlinear interaction plays a role on non-local transport and transient phenomena in fusion plasmas. Near future, these findings will be cooperated into the transport model for ITER plasma analysis.

  19. Experimental Study of Particle Heating and Acceleration by Use of Short Pulse Magnetic Reconnection Experiment and Two Dimensional Image Diagnostics

    Grant number:19340172  2007 - 2009

    ONO Yasushi

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    Authorship:Coinvestigator(s) 

    We directly measured for the first time particle heating and acceleration of magnetic reconnection using short-pulse/high magnetic field merging experiment and 2-D image diagnostics of magnetic field, ion temperature and electron temperature. We found plasma acceleration to 70-80% of Alfven speed by reconnection outflow, selective ion heating by fast shock at two down-stream of reconnection outflow and electron heating by ohmic heating of current sheet.

  20. Multi-physics Plasma Dynamics with Macro-Micro Interlocked Simulations

    Grant number:19340180  2007 - 2009

    Japan Society for the Promotion of Science  Grants-in-Aid for Scientific Research Grant-in-Aid for Scientific Research (B)  Grant-in-Aid for Scientific Research (B)

    KUSANO Kanya, KAGEYAMA Akira, MIYOSHI Takahiro, SATO Tetsuya, HIROSE Shigenobu, SUGIYAMA Tooru, HASEGAWA Hiroki, SHIMA Shinーichiro, KAWANO Akio, KISHIMOTO Yasuaki, YAGI Masatoshi, ISHIHARA Osamu, INOUE Satoshi, KAGEYAMA Akira, MIYOSHI Takahiro, SATO Tetsuya, HIROSE Shigenobu, SUGIYAMA Tooru, HASEGAWA Hiroki, SHIMA Shinーichiro, KAWANO Akio, KISHIMOTO Yasuaki, YAGI Masatoshi, ISHIHARA Osamu, INOUE Satoshi

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    Authorship:Principal investigator 

    Grant amount:\16640000 ( Direct Cost: \12800000 、 Indirect Cost:\3840000 )

    The macro-micro interlocked (MMI) simulation is a new framework of numerical simulation, which is capable to deal with the interaction of multi-scale and multi-physics phenomena. In this study, we have developed the basic algorithm of the MMI simulation, and applied it to solar and space plasmas including solar flare and coronal mass ejection, as well as to the formation of cloud, in order to advance the capability of numerical simulations. In addition, we have developed the study for space weather forecasting with the MMI simulation.

  21. 宇宙天気予報の基礎研究

    2005.4 - 2010.3

    科学研究費補助金 

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    Authorship:Coinvestigator(s) 

  22. Basic Study of Space Weather Prediction

    Grant number:17GS0208  2005 - 2009

    Japan Society for the Promotion of Science  Grants-in-Aid for Scientific Research Grant-in-Aid for Creative Scientific Research  Grant-in-Aid for Creative Scientific Research

    SHIBATA Kazunari, SEKII Takashi, KUSANO Kanya, FUJIKI Kenichi, OGINO Tatuki, HOSHINO Masahiro, SHINOHARA Iku, UGAI Masayuki, KATOU Seiichi, OHMURA YOshiharu, MURATA Takeshi, FUJIMOTO Masaki, TSUNETA Saku, OBARA Takahiro, SEKII Takashi, KUSANO Kanya, FUJIKI Kenichi, OGINO Tatuki, HOSHINO Masahiro, SHINOHARA Iku, UGAI Masayuki, KATOU Seiichi, OHMURA YOshiharu, MURATA Takeshi, FUJIMOTO Masaki, TSUNETA Saku, OBARA Takahiro

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    Authorship:Coinvestigator(s) 

    Space weather prediction is an urgent issue for modern civilization. Basic study of space weather prediction has been carried out, by developing the numerical multi-scale coupling model for the system from the Sun to the Earth on the basis of the new observations. This study was pushed as a part of CAWSES (Climate And Weather of the Sun-Earth system) program for 5 years, to encourage active communication and collaboration between solar physicists and geophysicists both in Japan and international communities.

  23. 太陽および宇宙プラズマにおける磁気ヘリシティのダイナミクスに関する研究

    2004.4 - 2007.3

    科学研究費補助金  基盤研究(C)

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    Authorship:Principal investigator 

  24. Study of Magnetic Helicity Dynamics in Solar and Space Plasmas

    Grant number:16540216  2004 - 2006

    Japan Society for the Promotion of Science  Grants-in-Aid for Scientific Research Grant-in-Aid for Scientific Research (C)  Grant-in-Aid for Scientific Research (C)

    KUSANO Kanya, MIYOSHI Takahiro, MIYOSHI Takahiro

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    Grant amount:\3400000 ( Direct Cost: \3400000 )

    Magnetic helicity is a physical variable, which can quantify the total linking number of magnetic field flux. Since magnetic helicity is a conserved quantity in the ideal magnetohydrodynamic (MHD) process, and is a proxy of magnetic free energy, it is widely believed that magnetic helicity may play a role as tracer and driver of MHD activities. We have investigated the dynamics of magnetic helicity in the Sun-Earth connection system. First, we have developed the methodology to measure magnetic helicity flux across the solar surface based on the madnetogram observation, and found that the helicity injection into the solar corona is well correlated with the soft X-ray emission activity in the solar corona. Second, we have developed the new numerical tool to reconstruct the three-dimensional magnetic field in the solar corona from vector magnetogram, and applied it to the data provided by the new solar satellite observatory HINODE.. As a result, we have revealed that magnetic field in pre-flare phase indeed has a sheared structure, which is well consistent with the paring of two-ribbon appearing after the onset of flare. Third, we created the state-of-the-art numerical scheme for ideal MHD equation, called HUD scheme, and have demonstrated that the computational performance of HLLD scheme is better than any previous schemes for the accuracy, robustness, efficiency and handiness of computation. Finally, we have applied the HLLD scheme to the solar coronal simulation, which fully includes the spherical geometry, as well as to the magnetospheric simulation, in which more generic equation of state is taken into account. The solar coronal simulation has revealed that the critical magnetic helicity to drive the onset of coronal mass ejection (CME) is sensitive to the spatial structure of magnetic helicity injection.

  25. 高感度GeVγ線観測で探る巨大ブラックホールの進化とジェットの放出機構

    Grant number:14079206  2002 - 2006

    日本学術振興会  科学研究費助成事業 特定領域研究  特定領域研究

    深沢 泰司, 大杉 節, 川端 弘治, 水野 恒史, 片桐 秀明, 吉田 勝一, 草野 完也, 大杉 節, 川端 弘治, 水野 恒文, 片桐 秀明, 吉田 勝一, 草野 完也

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    本研究は、2008年度打ち上け予定の国際ガンマ線観測衛星GLASTによる巨大ブラックホールの進化とジェットの放出機構を探るために、その研究体制を構築することを目的とする。これまでのハードウエアーの設計、製作、試験に引き続いて、衛星に搭載された状態での環境試験による性能のモニターを続け、特に問題はなかった。今後の衛星打ち上け前後での性能モニターのために、各種モニター体制の確立を進めた。また、本年度購入したセンサーを用いて、上空でのハードウエアーの動作を理解するための簡易検出器を組み立てた。
    この他、本年度は特に、衛星運用の体制の立ち上げ、観測体制の立ち上げ、整備、他波長との連携の強化、データ解析体制の立ち上げ、などに力を入れて行った。衛星運用の予行演習にも参加し、衛星運用で想定される作業の見積もりを行った。GLASTの天体は他波長の情報も放射メカニズムの特定のためには非常に重要であるため、GLASTと他の波長との同時観測を行うための連携体制を進め、その一環として1つの天体の多波長連携観測の予行演習に広島大学に設置した可視光近赤外かなた望遠鏡も参加した。また、かなた望遠鏡によって同時観測する価値のある天体の試験観測を始めて、観測の戦略を練った。さらに、日本のX線天文衛星すざくとの連携観測も狙い、観測提案や、すざくの全天軟ガンマ線モニターの観測システムの整備を進めた。データ解析を打ち上げ直後に迅速に行うため、PCクラスタやディスクアレイの整備を進め、シミュレーション観測データを用いて解析を行い、解析ソフトの長所短所や系統誤差、解析手法の確立を行った。
    以上のようにGLASTの打ち上げ(2008年5月16日予定)に備えて研究体制を整えて、first lightを待つばかりである。

  26. 実データシミュレーションによる太陽コロナ活動の機構解明

    2000.4 - 2004.3

    科学研究費補助金  基盤研究(C)

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  27. Study of Activity Mechanism in the Solar Corona Based on Realistic-Data Simulations

    Grant number:12640236  2000 - 2003

    Japan Society for the Promotion of Science  Grants-in-Aid for Scientific Research Grant-in-Aid for Scientific Research (C)  Grant-in-Aid for Scientific Research (C)

    KUSANO Kannya, YOKOYAMA Takaaki, YOKOYAMA Takaaki

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    Authorship:Principal investigator 

    Grant amount:\3600000 ( Direct Cost: \3600000 )

    This project was carried out aiming to reveal the physical mechanism of the solar coronal energetic activity in terms of the combination of the detail observation of solar magnetic field by vector magnetographs and the three-dimensional numerical simulations. The following important results are obtained. (1)We developed a new methodology, which enables the measurement of magnetic helicity flux across the photospheric surface. (2)We found a clear correlation between the magnetic helicity flux across the photosphere and the soft X-ray energy flux out of the solar corona. (3)We revealed that the reversal of magnetic shear activates the energy liberation of the solar coronal magnetic field. (4)Based on the results above, we proposed a new flare model called "Reversed-Shear Flare Model", and examined the validity of that using the three-dimensional numerical simulations. (5)We investigated the spatial correlation between the magnetic shear structure and the brightening in pre-flare phases, and revealed that the initial bright points were located at the shear inversion line, as the Reversed-Shear Flare Model predicted. These results demonstrate the hypothesis that the magnetic helicity flux across the photosphere can play a cause of the solar coronal activity. In particular, it should be noted that the Reversed-Shear Flare Model can explain several important features seen in observation of solar flares. However, the development of the three-dimensional simulation only using realistic data is not yet completed, and remains for future works.

  28. 電磁流体力学的カタストロフの理論的研究

    1997.4 - 1999.3

    科学研究費補助金  奨励研究(A)

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  29. 電磁流体力学的カタストロフの理論的研究

    Grant number:09780438  1997 - 1998

    日本学術振興会  科学研究費助成事業 奨励研究(A)  奨励研究(A)

    草野 完也

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    Grant amount:\2000000 ( Direct Cost: \2000000 )

    高温プラズマではしばしば、磁気エネルギーが熱および運動エネルギーに突発的に変換される現象が観測される。本研究ではこうした電磁流体力学的カタストロフ過程の物理を、最小エネルギー原理と数値シミュレーションに基づいて研究した。本研究においては、太陽コロナにおける典型的な磁場配位である磁気ループシステムを念頭に置き、太陽表面運動が磁気ヘリシティをシステム内部へ供給する場合の非線形ダイナミクスを計算した。その結果、磁気レイノルズ数の大小によって2つの異なるダイナミクスが発生することが明らかになった。磁気レイノルズ数が小さな場合、供給されたヘリシティは拡散によって失われる定常的な拡散平衡状態が実現する。しかし、磁気レイノルズ数の増加に伴い、拡散平衡状態の磁気ヘリシティも増加するため、磁気ヘリシティが臨界値を越えるとシステムは磁気アーケードモードに対して不安定となる。それゆえ、磁気レイノルズ数が大きな場合、蓄積された磁気ヘリシティは不安定性の結果としての磁気リコネクションを通してシステムの外に放出される。この過程は磁気ヘリシティの供給がある限り続き、ダイナミクスはある種のリミットサイクルを描く。その結果、磁気ループ内部の磁気ヘリシティ量の増加は磁気レイノルズ数の増加と共に飽和してしまう。すなわち、磁気レイノルズ数の大きな高温プラズマでは、間欠的なヘリシティ放出が能動的に生じるため、蓄積できる磁気ヘリシティの容量は有限の値に制限されることがわかった.

  30. MHD平衡解の分岐遷移過程に現れる電流シ-トの構造安定性

    1996.4 - 1997.3

    科学研究費補助金  奨励研究(A)

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  31. MHD平衡解の分岐遷移過程に現れる電流シートの構造安定性

    Grant number:08780452  1996

    日本学術振興会  科学研究費助成事業 奨励研究(A)  奨励研究(A)

    草野 完也

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    Authorship:Principal investigator 

    Grant amount:\1000000 ( Direct Cost: \1000000 )

    磁気閉じ込め核融合炉心や太陽コロナのような高磁気レイノルズ数、低プラズマβにあるプラズマシステムにおいては、短時間に大規模なエネルギーが突然解放される現象がしばしば観測される。本研究においてはこうした突発的なエネルギー解放現象をMHD平衡解の遷移過程として捉えた上で、この遷移過程に現れる電流シートの安定性と平衡遷移過程との関係を数値シミュレーションをもとに調べた。特に、太陽フレアを念頭におき、太陽コロナ磁気ループ不安定性の結果として形成される電流シートの安定性を詳しく調べた。その結果、磁気レイノルズ数の平方根に比例して電流シートのアスペクト比A(=長さ/幅)は増加するが、Aが10^2に達すると、電流シートはテアリング不安定性に対して不安定になることが明らかにされた。その結果、電流シートの中に複数のX点(磁気中性点)が出現し、磁気島が形成されるフェーズと、磁気島が電流シートに沿って排出されるフェーズが交互に現れることが分かった。電流シートの不安定性の成長率は電流シート形成の原因である磁気ループ不安定の成長率よりも大きい。それ故、電流シートの不安定化はシステムの不安定化を促進し、不安定性は指数関数よりも早く爆発的に成長することが明らかにされた。こうした爆発的不安定は磁気レイノルズ数が10^4よりも小さな時には生じないことから、高温プラズマに特徴的な現象であると考えられる。上記の数値シミュレーションの結果は、太陽フレアにおけるX線観測結果と非常によい形状的一致を示しており、太陽フレアの重要な物理機構を捉えていると思われる。また、これらの結果はトカマクの鋸歯状振動に関するKadmtsevのスケーリングが高磁気レイノルズ数領域では成り立たないことを示唆するものである。

  32. 太陽コロナにおける爆発的エネルギ-解放過程に関する統一的分岐理論

    1995.4 - 1996.3

    科学研究費補助金  奨励研究(A)

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  33. 太陽コロナにおける爆発的エネルギー解放過程に関する統一的分岐理論

    Grant number:07740188  1995

    日本学術振興会  科学研究費助成事業 奨励研究(A)  奨励研究(A)

    草野 完也

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    Authorship:Principal investigator 

    Grant amount:\900000 ( Direct Cost: \900000 )

    本研究においては,太陽コロナにおける爆発的エネルギー解放過程を最小エネルギー解の分岐と遷移のダイナミクスとして統一的に理解するための理論研究を行った。特に、本年は研究実施計画に基づきTaylorの変分原理から求まる、線形無力平衡配位の安定性解析、およびそこで見い出された不安定性の非線形ダイナミクスに関する数値シミュレーションを実施した。その結果、以下の事項が明らかにされた。
    1.磁気ヘリシティがrotオペレターの非結合固有値に対応する臨界ヘリシティよりも大きい場合、太陽コロナにおける線形無力配位は複数の解に分岐する。この時、エネルギーの高いブランチは抵抗性MHDモードに対して不安定である。
    2.この不安定性の成長が非線形領域に達すると、磁気ループ中央に電流シートが形成され、磁気再結合を結果する。磁気再結合はテイラー状態の分岐理論が予言するように磁気ループを上下に分離する。
    3.磁気再結合における電流シートの長さは幾何学的制約から磁気ループの幅程度であり、電気抵抗に寄らない。一方、その幅は電気抵抗の平方根に比例する。また、電流シート上の最大加熱率も電気抵抗に寄らない。
    4.真空磁場に光球面運動によって徐々に磁気ヘリシティを注入した場合、不安定性と磁気ヘリシティ注入の競争過程として、ダイナミクスが決められる。それゆえ、磁気レイノルズ数が大きいほど大量の磁気ヘリシティ注入が行われ、その後の磁気再結合によるエネルギー解放はより爆発的に実現される。
    以上の結果は、太陽フレアの爆発性を分岐解の遷移として一般的に理解する事が出来る可能性を強く示唆している。重力効果を含めた拡張された分岐理論の構築は時間的制約から将来に持ち越された。

  34. 開いたMHDシステムにおける動的構造の研究

    1994.4 - 1995.3

    科学研究費補助金  奨励研究(A)

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  35. 開いたMHDシステムにおける動的構造の研究

    Grant number:06780392  1994

    日本学術振興会  科学研究費助成事業 奨励研究(A)  奨励研究(A)

    草野 完也

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    Authorship:Principal investigator 

    Grant amount:\900000 ( Direct Cost: \900000 )

    本研究においては、特に太陽コロナを念頭に置き、磁気ヘリシティおよび磁気エネルギーをシステムの外から供給されたMHDシステムの非線形応答に関する数値的理論的考察を行った。
    (1)数値シミュレーション研究:以下のような3次元MHDシミュレーションを実施した。計算領域である直方体をコロナ、ある境界面を両極性の磁束領域が存在する太陽表面と考える。磁束領域では回転運動が計算領域内部に磁気ヘリシティと磁気エネルギーを注入する。計算の結果、真空磁場を初期条件に取った場合、内部の磁束管がゆっくり巻き上げられる準定常的変化の後、多くの磁束管が再結合を受ける大規模エネルギー緩和が発生することが明らかにされた。
    (2)最小エネルギー解の分岐理論:上のシミュレーション結果を物理的に説明するため、J.B.Taylorの最小エネルギー原理を開いたシステムに拡張する理論を構築した。その結果、最小エネルギー状態はヘリシティの供給量とその結果による磁束構造の幾何学的変化によって2つの解に分岐することが示された。分岐した解の遷移過程がシミュレーションにおける大規模エネルギー緩和に対応する事を明らかにした。分岐によって新しく現れる解は他の解と事なる磁気トポロジーを持つためその遷移過程に磁気再結合を伴う。
    (3)新しい太陽フレアモデルの提唱:以上の結果から開いたMHDシステムがヘリシティの供給によって間欠的なエネルギー緩和をすることを分岐理論によって明らかにすると共に、太陽フレアの物理機構が分岐した最小エネルギー解の遷移として説明できることを提唱した。

  36. セルフコンシステントなダイナモ過程の理論シミュレ-ション研究

    1993.4 - 1994.3

    科学研究費補助金  奨励研究(A)

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  37. セルフコンシステントなダイナモ過程の理論シミュレーション研究

    Grant number:05780360  1993

    奨励研究(A)

    草野 完也

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    Authorship:Principal investigator 

    Grant amount:\900000 ( Direct Cost: \900000 )

    ダイナモ過程は電磁流体の運動エネルギーを源とする磁気エネルギーの再生機構であると共に、磁場構造の自己組織化過程とみなすこともできる。本研究では、数値シミュレーション手法を駆使し、高非線型領域において定常的構造を持つダイナモ解が周期的構造あるいは非周期的構造を持つ解にそれぞれ分岐する可能性及びその条件を調べた。研究成果は以下の通りである。
    (1)回転球殻中の熱対流および2重拡散対流に関する並列化3次元シミュレーションコードを開発し、シミュレーションを実施した。
    (2)テイラー数T=1^05、プランドル数P=1の場合、臨界レーリー数近傍の対流は南北にそった3対の定常的に西向きヘドリフトするロールとなる。レーリー数が増加すると、臨海レーリー数の3倍程度で解は定常解から非定常解へ遷移する。非定常解は3対のロール解と4対のロール解が非周期的に交互に支配的になる時間的挙動を示す。
    (3)2重拡散対流の場合、ドリフトロール解と周期振動解の重ね合わせで記述できる解が出現する。レーリー数を増加させると、振動解の振幅が次第に増加する。さらにレーリー数を大きくすると、ロールのドリフトの向きが東側へ変る。
    (4)対流シミュレーションで得られた速度場を使い、運動学的ダイナモモデルによる固有値計算を行なった。その結果、双極子解の固有値が4重極子解の固有値より大きいことを見いだした。

  38. 磁気リコネクションによるプラズマの超加速過程

    1992.4 - 1993.3

    科学研究費補助金  奨励研究(A)

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  39. 自由境界プラズマ不安定性の非線型発展とMHD緩和過程

    1989.4 - 1990.3

    科学研究費補助金  奨励研究(A)

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  40. Theory and Simulation Study of Transport Processes in Magnetized Plasmas

    Grant number:01580012  1989 - 1990

    Grant-in-Aid for General Scientific Research (C)

    NISHIKAWA Kyoji

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    The purpose of the present research is to study the particle and energy transport of a magnetically confined plasma across the magnetic field over a macroscopic scale based on the particle kinetic theory. One useful method for this purpose is to use the particle simulation technique. To this end, the macroscale particle code which is applicable to study nonuniform and nonlinear plasma behaviors over a long time and large space scales has been developed. The development of the macroscale particle simulation code was started in 1984 and was completed in the fiscal year 1989 for the case of a plasma in nearly uniform density and magnetic field profile. In the fiscal year 1990, an improvement of this code was carried out with the aim to make it applicable to study of macroscopic and kinetic nonlinear phenomena in non-uniform high temperature plasmas. Namely, there are three requisits : 1) t he characteristic time scale be much larger than the electronic time scales (DELTAt>>omega_<CA>^<-1>, omega_<PA>^<-1>) ; 2) strong nonuniformity of the density and magnetic field be treated ; 3) arbitrary plasma shapes such as torus, noncirculer cross sections be treated. Of these, condition 1) was already satisfied, so the code was improved to satisfy condition 2) in 1990. Further improvement and applications to real systems are left to future work which will be conducted at the newly established National Institute for Fusion Science.
    As for the analytical work, a general expression for the particle drift flux across an arbitrary shape of magnetic field due to the ponderomotive force of high frequency electromagnetic fields was derived based on the single particle picture and was shown to be consistent with the flux based on the fluid picture. The nonambipolr flux which causes a radial electric field was derived.

  41. 計算機実験による磁気再結合の物理に関する総合的研究

    1988.4 - 1989.3

    科学研究費補助金  奨励研究(A)

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    Authorship:Principal investigator 

  42. 逆転磁場ピンチプラズマにおける緩和過程

    1986.4 - 1988.3

    科学研究費補助金  奨励研究(A)

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  43. First Principle Simulation of Cloud and Aerosol Formation

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    Grant type:Competitive

  44. Theoretical Study of Magnetic Reconnection

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    Grant type:Competitive

  45. The Understanding of Solar and Planetary Dynamo

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    Grant type:Competitive

  46. The Understanding and Prediction of Solar Flare Onset

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    Grant type:Competitive

  47. Self-organization of Plasmas

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    Grant type:Competitive

  48. Modelings of Space Weather and Space Climate

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    Grant type:Competitive

  49. Macro- and Micro-Interlocked Simulation of Multi-scale Dynamics

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    Grant type:Competitive

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Teaching Experience (On-campus) 4

  1. 先端物理学基礎Ⅲ

    2011

  2. プラズマ宇宙物理学

    2011

  3. 先端物理学基礎Ⅲ

    2010

  4. プラズマ宇宙物理学

    2010

Teaching Experience (Off-campus) 2

  1. 2009.4 - 2010.3 東京工業大学)

  2. 2009.4 - 2010.3 名古屋工業大学)

 

Social Contribution 11

  1. 第20回公開セミナー「天文学の最前線」

    2011.8

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    名古屋市科学館にて公開セミナー「天文学の最前線」を実施し「太陽の謎に挑む現代天文学」について講演すると共に、名古屋大学の天文学研究について説明した。

  2. 太陽研究最前線体験ツアー2011

    2011.8

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    国立天文台、京都大学、東京大学と協力し、全国の理系大学生を対象に国内の代表的な太陽研究施設を公開すると共に、太陽研究の最前線を説明する連続セミナーを開催した。

  3. お寺で宇宙学

    2011.2

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    想念寺(名古屋市)にて一般市民を対象に、仏教と科学の関係を考える公開セミナー「お寺で宇宙学」を実施し、「テラで考えるミクロとマクロ~階層的世界は錯覚か?~」について講演した。

  4. 名古屋大学オープンカレッジ

    2010.12

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    一般市民を対象とした公開講座「母なる星 太陽の不思議な素顔」を実施した。

  5. 太陽地球環境研究所20周年記念一般講演会

    2010.11

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    太陽地球環境研究所創立20周年を記念した一般講演会において「太陽の謎~ガリレオから未来へ~」と題した講演を行った。

  6. 海洋研究開発機構サイエンスカフェ

    2010.11

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    海洋研究開発機構横浜研究所の一般公開にて実施されたサイエンスカフェにて「宇宙と地球環境の不思議な関係」について解説した。

  7. 太陽オーロラウィーク2010 陸別町

    2010.10

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    陸別町銀河の森天文台においてアラスカ上空のオーロラをインタネットで中継すると共に、太陽とオーロラの関係について一般市民の疑問に答える質問コーナーを開催した。

  8. 太陽研究最前線体験ツアー2010

    2010.8

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    国立天文台、京都大学、東京大学と協力し、全国の理系大学生を対象に国内の代表的な太陽研究施設を公開すると共に、太陽研究の最前線を説明する連続セミナーを開催した。

  9. 太陽研究最前線体験ツアー2009

    2009.11

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    国立天文台、京都大学、東京大学と協力し、全国の理系大学生を対象に国内の代表的な太陽研究施設を公開すると共に、太陽研究の最前線を説明する連続セミナーを開催した。

  10. セルバンテス文化センター東京 ソルプレサス・デル・コスモス(宇宙の驚異)

    2009.10

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    カナリアス宇宙物理研究所とインタネットで接続し、スペインと日本の天文学者と共に宇宙物理学の最前線について一般市民に講演した。

  11. 国立天文台レクチャー

    2009.6

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    太陽活動と地球環境の関係に関して報道関係者へ説明した。

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