2022/03/21 更新

写真a

ノセ マサヒト
能勢 正仁
NOSÉ Masahito
所属
宇宙地球環境研究所 基盤研究部門 電磁気圏研究部 准教授
大学院担当
大学院工学研究科
職名
准教授
連絡先
メールアドレス
外部リンク

学位 3

  1. 博士(理学) ( 1998年3月   京都大学 ) 

  2. 修士(理学) ( 1995年3月   京都大学 ) 

  3. 学士(理学) ( 1993年3月   京都大学 ) 

研究キーワード 6

  1. 宇宙惑星科学

  2. 超高層物理学

  3. 宇宙空間物理学

  4. 地球電磁気学

  5. データサイエンス

  6. 情報学

研究分野 2

  1. 情報通信 / データベース  / 情報地球物理学

  2. 自然科学一般 / 宇宙惑星科学  / 宇宙空間物理学、地球電磁気学、超高層物理学

現在の研究課題とSDGs 2

  1. 宇宙環境擾乱現象の発生機構解明およびその予測

  2. 研究データマネジメント

経歴 6

  1. 名古屋大学   宇宙地球環境研究所   准教授

    2018年8月 - 現在

  2. 京都大学   理学研究科附属地磁気世界資料解析センター   助教

    2007年4月 - 2018年7月

  3. 京都大学   理学研究科附属地磁気世界資料解析センター   助手

    2001年4月 - 2007年3月

  4. ジョンズホプキンス大学   応用物理研究所   研究員

    1998年7月 - 2001年3月

  5. 京都大学大学院理学研究科・研修員

    1998年4月 - 1998年6月

  6. 日本学術振興会特別研究員

    1996年4月 - 1998年3月

▼全件表示

学歴 3

  1. 京都大学   理学研究科   地球惑星科学専攻

    1995年4月 - 1998年3月

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    国名: 日本国

  2. 京都大学   理学研究科   地球物理学専攻

    1993年4月 - 1995年3月

  3. 京都大学   理学部

    1989年4月 - 1993年3月

所属学協会 3

  1. 地球電磁気・地球惑星圏学会

  2. 日本地球惑星科学連合

  3. アメリカ地球物理学連合(American Geophysicul Union)

受賞 1

  1. 大林奨励賞(第24号)

    2006年11月   地球電磁気・地球惑星圏学会   ウェーブレット関数を用いたPi2脈動の自動検出手法の開発とその応用研究

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    受賞区分:国内学会・会議・シンポジウム等の賞  受賞国:日本国

 

論文 179

  1. Flux enhancements of field-aligned low-energy O+ ion (FALEO) in the inner magnetosphere: A possible source of warm plasma cloak and oxygen torus 査読有り 国際共著

    Nosé, M., A. Matsuoka, Y. Miyoshi, K. Asamura, T. Hori, M. Teramoto, I. Shinohara, M. Hirahara, C. A. Kletzing, C. W. Smith, R. J. MacDowall, H. E. Spence, G. D. Reeves, and J. W. Gjerloev

    Journal of Geophysical Research     2022年3月

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    担当区分:筆頭著者   記述言語:英語   掲載種別:研究論文(学術雑誌)  

    DOI: 10.1029/2021JA030008

  2. Off-Equatorial Pi2 Pulsations Inside and Outside the Plasmapause Observed by the Arase Satellite

    Teramoto M., Miyoshi Y., Matsuoka A., Kasahara Y., Kumamoto A., Tsuchiya F., Nosé M., Imajo S., Shoji M., Nakamura S., Kitahara M., Shnohara I.

    Journal of Geophysical Research: Space Physics   127 巻 ( 1 )   2022年1月

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    記述言語:日本語   掲載種別:研究論文(学術雑誌)   出版者・発行元:Journal of Geophysical Research: Space Physics  

    Using magnetic field and electron density data from the Arase satellite for the period from March 2017 to September 2019, we investigate the spatial properties of Pi2 pulsations in relation to the plasmapause over a wide latitudinal range (absolute magnetic latitude, |Mlat|, < 45°) in the inner magnetosphere. Magnetic field disturbances that have high coherence (> 0.7) with Pi2 pulsations in the north-south (H) component at low-latitude ground stations on the nightside, are dominantly identified from the magnetic fields in the radial (BR) and compressional (BP) components when the satellite is in the pre-midnight sector. In particular, high-coherence BP events are distributed over wide L-values and latitudinal ranges on the nightside in the pre-midnight sector. We identify the location of the plasmapause using the electron densities measured by Arase, and found that the BP-H power ratio and the cross phases of the high-coherence events show a gradual peak and a clear phase change from 0° to 180° in the vicinity of the plasmapause, respectively. These features indicate that mid- and low-latitude Pi2 pulsations on the nightside are excited by the plasmaspheric virtual resonance mode.

    DOI: 10.1029/2021JA029677

    Scopus

  3. Special issue “International Geomagnetic Reference Field: the thirteenth generation”

    Alken P., Thébault E., Beggan C.D., Nosé M.

    Earth, Planets and Space   74 巻 ( 1 )   2022年1月

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    記述言語:日本語   掲載種別:研究論文(学術雑誌)   出版者・発行元:Earth, Planets and Space  

    DOI: 10.1186/s40623-021-01569-z

    Scopus

  4. Preferential Energization of Lower-Charge-State Heavier Ions in the Near-Earth Magnetotail

    Keika K., Kasahara S., Yokota S., Hoshino M., Seki K., Amano T., Kistler L.M., Nosé M., Miyoshi Y., Hori T., Shinohara I.

    Journal of Geophysical Research: Space Physics   127 巻 ( 1 )   2022年1月

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    記述言語:日本語   掲載種別:研究論文(学術雑誌)   出版者・発行元:Journal of Geophysical Research: Space Physics  

    O+ ions make a significant contribution to plasma pressure in the inner magnetosphere during magnetic storms. The storm-time O+ enhancements are primarily caused by enhanced supply from the ionosphere and preferential energization in the magnetotail. In order to characterize the magnetotail process that dominates the energization, we examine differences in energy spectra of energetic 10–180 keV/q ions between different ion species, namely H+, He++, He+. O++, and O+. We use observations made by the MEP-i instrument on the Arase (ERG) spacecraft on the nightside in the radial distance range of ∼5–∼7 Re during the main and early recovery phases of the May and July 2017 storms. The comparisons of energy spectra show that, for the same charge states, heavier ions are more energized than lighter ions. For the same mass, lower-charge-state ions are more energized than higher-charge-state ions. The spectra exhibit a sharp decrease at high energies for all ion species, while the spectra for more energized ions were shifted toward higher energies, compared to those for less energized ions. The results suggest that the preferential energization is due to temperature increases rather than the generation of energetic ions in the high-energy tail. Considering temporal and spatial scales of heavy ion kinetic motions, we conclude that the preferential energization of lower-charge-state heavier ions occurs during the course of dipolarization, likely due to non-adiabatic heating in the near-Earth plasma sheet, effective trapping during transport by localized flow channels, and/or non-adiabatic acceleration within the near-Earth flow-braking region.

    DOI: 10.1029/2021JA029786

    Scopus

  5. Field-Aligned Electron Density Distribution of the Inner Magnetosphere Inferred From Coordinated Observations of Arase and Van Allen Probes

    Obana Yuki, Miyashita Yukinaga, Maruyama Naomi, Shinbori Atsuki, Nose Masahito, Shoji Masafumi, Kumamoto Atsushi, Tsuchiya Fuminori, Matsuda Shoya, Matsuoka Ayako, Kasahara Yoshiya, Miyoshi Yoshizumi, Shinohara Iku, Kurth William S., Smith Charles W., MacDowall Robert J.

    JOURNAL OF GEOPHYSICAL RESEARCH-SPACE PHYSICS   126 巻 ( 10 )   2021年10月

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    記述言語:日本語   掲載種別:研究論文(学術雑誌)   出版者・発行元:Journal of Geophysical Research: Space Physics  

    The Radiation Belt Storm Probes (RBSP) and the Arase satellites have different inclinations and sometimes they fly both near the equator and off the equator on the same magnetic field line simultaneously. Such conjunction events give us opportunities to compare the electron density at different latitudes. In this study, we analyzed the plasma waves observed by Arase and RBSP during the three conjunction events during and after the September 7, 2017 storm. The electron number density at the satellite positions was estimated from frequencies of the Upper Hybrid Resonance emissions obtained by the High Frequency Analyzer of the Plasma Wave Experiment onboard the Arase and the Waves instrument onboard the RBSP, respectively. During the three conjunction events, the satellites passed through the plume, inner trough (the narrow region with low electron density between the main body of the plasmasphere and the plume), plasmatrough with variable electron density, and partially refilled plasmasphere. The power-law index m for the inner trough and plume was inferred to be 4–7 and ∼0, respectively. This is interpreted to mean that the trough was close to collisionless and the plume was relatively near diffusive equilibrium. In the plasmatrough with the varying density, both the high-density and low-density regions had m ∼ 0. The low-density portion of this region may have a different origin from the inner trough, because of the different m indices. For the partially refilled plasmasphere in the storm recovery phase, the power-law index m showed negative values, meaning that the density in the equatorial plane was higher than at higher latitudes.

    DOI: 10.1029/2020JA029073

    Web of Science

    Scopus

  6. Dayside Cusp Aurorae and Ionospheric Convection Under Radial Interplanetary Magnetic Fields

    Li Hsien-Ming, Shue Jih-Hong, Taguchi Satoshi, Nose Masahito, Hosokawa Keisuke, Ruohoniemi J. Michael, Zhang Yongliang, Wing Simon, Lester Mark

    JOURNAL OF GEOPHYSICAL RESEARCH-SPACE PHYSICS   126 巻 ( 5 )   2021年5月

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    記述言語:日本語   掲載種別:研究論文(学術雑誌)   出版者・発行元:Journal of Geophysical Research: Space Physics  

    Dayside cusp aurorae are created from particles precipitating into the cusp, and ionospheric convection is driven by solar wind electric fields. In this study, we coordinated the observations obtained from the all-sky camera on Svalbard, the Super Dual Auroral Radar Network, SuperMAG magnetometer data, and far ultraviolet imagers on board the Defense Meteorological Satellite Program satellites for the event January 4, 2014 to examine the morphology of aurorae and the patterns of ionospheric convection for radial interplanetary magnetic field (IMF). During the event, a poleward-moving auroral form and antisunward ionospheric convection were observed when the IMF turned into almost purely radial. Moreover, both types of antisunward and sunward convection were simultaneously observed near the footprint of the cusp at different times during the radial IMF period. The antisunward convection and sunward convection are typically an indicator of the dayside reconnection for the southward IMF and the lobe reconnection for the northward IMF, respectively. All those observations support the concept of low-latitude dayside and high-latitude lobe reconnection for the radial IMF. This study further shows that the coexistence of the two types of reconnection for radial IMF, resulting in an interplay of repetitive antisunward and sunward convection.

    DOI: 10.1029/2019JA027664

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    CiNii Research

  7. ジオスペース科学分野におけるデータ出版とデータ引用の現状およびそのプラクティス 査読有り

    能勢 正仁, 小山 幸伸

    論文誌トランザクションデジタルプラクティス   2 巻   頁: 9 - 20   2021年

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    記述言語:英語   掲載種別:研究論文(学術雑誌)  

    CiNii Research

  8. Penetration electric fields observed at middle and low latitudes during the 22 June 2015 geomagnetic storm

    Hashimoto K.K., Kikuchi T., Tomizawa I., Hosokawa K., Chum J., Buresova D., Nose M., Koga K.

    Earth, Planets and Space   72 巻 ( 1 )   2020年12月

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    記述言語:日本語   掲載種別:研究論文(学術雑誌)   出版者・発行元:Earth, Planets and Space  

    Prompt penetration electric fields were detected during the intense geomagnetic storm on 22 June, 2015 by the HF Doppler sounders at middle and low latitudes; Prague (Czech Republic), Iitate, Oarai, Onna (Japan), and Zhongli (Republic of China). The storm was initiated by the storm sudden commencement (SC) at 1833 UT, immediately followed by the main phase with the minimum SYM-H of − 139 nT at 2017 UT. The convection electric field was found to be up to 5.1 mV/m at low latitudes, which is enough to cause ionospheric disturbances such as the enhancement of the total electron content, equatorial ionization anomaly and so on. The electric fields of the SC and main phase are westward in the night (0330 MLT), while eastward in the evening (1930 MLT). The main phase electric field intensified the eastward equatorial electrojets (EEJ) at Huancayo in South America on the dayside (1330 MLT) and the westward EEJ on the nightside at Guam in the western Pacific (0330 MLT) and Tirunelveli in India (00 MLT). The eastward direction of the evening-time electric field agrees with a feature of the evening anomaly of the penetration electric field, while the intensity is suppressed because of the sunlit condition in the evening in the summer solstice. The sudden northward turning of the interplanetary magnetic field (IMF) caused a transition from the main phase to the recovery phase, when the EEJ turned into the counterelectrojet (CEJ). It was found that the HF Doppler sounders detected an impulsive eastward overshielding electric field at 2005 UT on the nightside during the northward IMF-driven CEJ with the duration of 17 min and intensity of 8.0 mV/m at Iitate (0500 MLT) and 11.8 mV/m at Prague (2130 MLT). The impulsive overshielding electric field was accompanied by the anti-sunward plasma flows at middle latitude (50°–60° GML) equatorward of the dusk sunward convection as observed with SuperDARN, which signifies intensification of the Region-2 field-aligned currents at the flow reversal. Substorm signatures are identified with intensified westward auroral electrojet and magnetic dipolarization as detected by the geosynchronous orbit satellite, ETS-VIII. Consequently, the stormtime substorm may provide strong overshielding electric fields to the middle latitude ionosphere on the nightside.[Figure not available: see fulltext.].

    DOI: 10.1186/s40623-020-01196-0

    Web of Science

    Scopus

  9. On the Transition Between the Inner and Outer Plasma Sheet in the Earth's Magnetotail

    Yukinaga Miyashita, Kanako Seki, Kaori Sakaguchi, Yasutaka Hiraki, Masahito Nosé, Shinobu Machida, Yoshifumi Saito, William R. Paterson

    Journal of Geophysical Research: Space Physics   125 巻 ( 4 )   2020年4月

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    記述言語:英語   掲載種別:研究論文(学術雑誌)   出版者・発行元:American Geophysical Union (AGU)  

    We have statistically studied the average structure and properties of the plasma sheet in the Earth's magnetotail at radial distances between R∼8 and 32 RE on the basis of ion, electron, and magnetic field data from the Geotail spacecraft. Here we discuss the transition between the inner plasma sheet and the outer plasma sheet near the equatorial plane. The ion and electron number densities, pressures, and energy fluxes at high energies, as well as the magnetic field, generally decrease with increasing radial distance from the Earth. The characteristics of the flux changes are reflected in the radial pressure gradients. If the transition between the inner and outer plasma sheet is determined by the radial pressure gradient change, the ion and electron transitions are located, on average, at R∼11 to 13 RE and R∼11 to 17 RE, respectively, at the midnight meridian. It is possible that the ion transition is located earthward of the electron transition. Furthermore, we have estimated the electric field, the electric and diamagnetic drift velocities, and the κ parameter (the square root of the ratio of the minimum curvature radius of the magnetic field line to the maximum gyroradius), which differ between the ion inner and outer plasma sheet.

    DOI: 10.1029/2019ja027561

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    CiNii Research

  10. データ引用を研究活動の新たな常識に:研究データ利活用協議会(RDUF)リサーチデータサイテーション小委員会の活動

    能勢 正仁

    国立国会図書館, カレントアウェアネス   345 巻   頁: 2 - 4   2020年

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    記述言語:英語   掲載種別:研究論文(学術雑誌)  

    CiNii Research

  11. 地磁気観測で探る宇宙空間環境変動

    能勢 正仁

    日本磁気学会報「まぐね」   15 巻   頁: 244 - 254   2020年

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    記述言語:英語   掲載種別:研究論文(学術雑誌)  

    CiNii Research

  12. Special issue “The 13th International Conference on Substorms”

    LaBelle J., Lessard M., Nosé M., Raeder J.

    Earth, Planets and Space   71 巻 ( 1 )   2019年12月

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    記述言語:日本語   掲載種別:研究論文(学術雑誌)   出版者・発行元:Earth, Planets and Space  

    DOI: 10.1186/s40623-019-0990-1

    Web of Science

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  13. Correction to: Simultaneous observation of auroral substorm onset in Polar satellite global images and ground-based all-sky images (Earth, Planets and Space, (2018), 70, 1, (73), 10.1186/s40623-018-0843-3)

    Ieda A., Kauristie K., Nishimura Y., Miyashita Y., Frey H.U., Juusola L., Whiter D., Nosé M., Fillingim M.O., Honary F., Rogers N.C., Miyoshi Y., Miura T., Kawashima T., Machida S.

    Earth, Planets and Space   71 巻 ( 1 )   2019年12月

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    記述言語:日本語   掲載種別:研究論文(学術雑誌)   出版者・発行元:Earth, Planets and Space  

    In the original publication of this article [1], some reference lines are missing in Fig. 5a and Fig. 6b(6). This correction shows the correct figures. The publisher apologizes to the readers and authors for the inconvenience. The original publication has been corrected.

    DOI: 10.1186/s40623-019-1053-3

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  14. Eastward Propagating Second Harmonic Poloidal Waves Triggered by Temporary Outward Gradient of Proton Phase Space Density: Van Allen Probe A Observation

    Yamamoto K., Nosé M., Keika K., Hartley D.P., Smith C.W., MacDowall R.J., Lanzerotti L.J., Mitchell D.G., Spence H.E., Reeves G.D., Wygant J.R., Bonnell J.W., Oimatsu S.

    Journal of Geophysical Research: Space Physics   124 巻 ( 12 ) 頁: 9904 - 9923   2019年12月

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    記述言語:日本語   掲載種別:研究論文(学術雑誌)   出版者・発行元:Journal of Geophysical Research: Space Physics  

    Two wave packets of second harmonic poloidal Pc 4 waves with a wave frequency of ~7 mHz were detected by Van Allen Probe A at a radial distance of ~5.8 RE and magnetic local time of 13 hr near the magnetic equator, where plasmaspheric refilling was in progress. Proton butterfly distributions with energy dispersions were also measured at the same time; the proton fluxes at 10–30 keV oscillated with the same frequency as the Pc 4 waves. Using the ion sounding technique, we find that the Pc 4 waves propagated eastward with an azimuthal wave number (m number) of ~220 and ~260 for each wave packet, respectively. Such eastward propagating high-m (m > 100) waves were seldom reported in previous studies. The condition of drift-bounce resonance is well satisfied for the estimated m numbers in both events. Proton phase space density was also examined to understand the wave excitation mechanism. We obtained temporal variations of the energy and radial gradient of the proton phase space density and find that temporal intensification of the radial gradient can generate the two wave packets. The cold electron density around the spacecraft apogee was >100 cm−3 in the present events, and hence the eigenfrequency of the Pc 4 waves became lower. This causes the increase of the m number which satisfies the resonance condition of drift-bounce resonance for 10–30 keV protons and meets the condition for destabilization due to gyrokinetic effect.

    DOI: 10.1029/2019JA027158

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  15. Simultaneous observation of auroral substorm onset in Polar satellite global images and ground-based all-sky images

    能勢 正仁, Kauristie Kirsti, Nishimura Yukitoshi, Miyashita Yukinaga, Frey Harald U., Juusola Liisa, Whiter Daniel, Nosé Masahito, Fillingim Matthew O., Honary Farideh, Rogers Neil C., Miyoshi Yoshizumi, Miura Tsubasa, Kawashima Takahiro, Machida Shinobu

    Earth, Planets and Space   ( 70 )   2018年5月

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    記述言語:英語   掲載種別:研究論文(学術雑誌)   出版者・発行元:Springer Nature  

    Substorm onset has originally been defined as a longitudinally extended sudden auroral brightening (Akasofu initial brightening: AIB) followed a few minutes later by an auroral poleward expansion in ground-based all-sky images (ASIs). In contrast, such clearly marked two-stage development has not been evident in satellite-based global images (GIs). Instead, substorm onsets have been identified as localized sudden brightenings that expand immediately poleward. To resolve these differences, optical substorm onset signatures in GIs and ASIs are compared in this study for a substorm that occurred on December 7, 1999. For this substorm, the Polar satellite ultraviolet global imager was operated with a fixed-filter (170 nm) mode, enabling a higher time resolution (37 s) than usual to resolve the possible two-stage development. These data were compared with 20-s resolution green-line (557.7 nm) ASIs at Muonio in Finland. The ASIs revealed the AIB at 2124:50 UT and the subsequent poleward expansion at 2127:50 UT, whereas the GIs revealed only an onset brightening that started at 2127:49 UT. Thus, the onset in the GIs was delayed relative to the AIB and in fact agreed with the poleward expansion in the ASIs. The fact that the AIB was not evident in the GIs may be attributed to the limited spatial resolution of GIs for thin auroral arc brightenings. The implications of these results for the definition of substorm onset are discussed herein.

  16. The ARASE (ERG) magnetic field investigation

    能勢 正仁, Teramoto Mariko, Nomura Reiko, Nosé Masahito, Fujimoto Akiko, Tanaka Yoshimasa, Shinohara Manabu, Nagatsuma Tsutomu, Shiokawa Kazuo, Obana Yuki, Miyoshi Yoshizumi, Mita Makoto, Takashima Takeshi, Shinohara Iku

    Earth, Planets and Space   ( 70 )   2018年3月

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    記述言語:英語   掲載種別:研究論文(学術雑誌)   出版者・発行元:Springer Nature  

    The fluxgate magnetometer for the Arase (ERG) spacecraft mission was built to investigate particle acceleration processes in the inner magnetosphere. Precise measurements of the field intensity and direction are essential in studying the motion of particles, the properties of waves interacting with the particles, and magnetic field variations induced by electric currents. By observing temporal field variations, we will more deeply understand magnetohydrodynamic and electromagnetic ion-cyclotron waves in the ultra-low-frequency range, which can cause production and loss of relativistic electrons and ring-current particles. The hardware and software designs of the Magnetic Field Experiment (MGF) were optimized to meet the requirements for studying these phenomena. The MGF makes measurements at a sampling rate of 256 vectors/s, and the data are averaged onboard to fit the telemetry budget. The magnetometer switches the dynamic range between ± 8000 and ± 60, 000 nT, depending on the local magnetic field intensity. The experiment is calibrated by preflight tests and through analysis of in-orbit data. MGF data are edited into files with a common data file format, archived on a data server, and made available to the science community. Magnetic field observation by the MGF will significantly improve our knowledge of the growth and decay of radiation belts and ring currents, as well as the dynamics of geospace storms.

  17. Theory, Modeling, and Integrated studies in the Arase (ERG) project

    海老原 祐輔, 大村 善治, Ebihara Yusuke, Katoh Yuto, Amano Takanobu, Saito Shinji, Shoji Masafumi, Nakamizo Aoi, Keika Kunihiro, Hori Tomoaki, Nakano Shin'ya, Watanabe Shigeto, Kamiya Kei, Takahashi Naoko, Omura Yoshiharu, Nose Masahito, Fok Mei-Ching, Tanaka Takashi, Ieda Akimasa, Yoshikawa Akimasa

    Earth, Planets and Space   ( 70 )   2018年2月

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    記述言語:英語   掲載種別:研究論文(学術雑誌)   出版者・発行元:Springer Nature  

    Understanding of underlying mechanisms of drastic variations of the near-Earth space (geospace) is one of the current focuses of the magnetospheric physics. The science target of the geospace research project Exploration of energization and Radiation in Geospace (ERG) is to understand the geospace variations with a focus on the relativistic electron acceleration and loss processes. In order to achieve the goal, the ERG project consists of the three parts: the Arase (ERG) satellite, ground-based observations, and theory/modeling/integrated studies. The role of theory/modeling/integrated studies part is to promote relevant theoretical and simulation studies as well as integrated data analysis to combine different kinds of observations and modeling. Here we provide technical reports on simulation and empirical models related to the ERG project together with their roles in the integrated studies of dynamic geospace variations. The simulation and empirical models covered include the radial diffusion model of the radiation belt electrons, GEMSIS-RB and RBW models, CIMI model with global MHD simulation REPPU, GEMSIS-RC model, plasmasphere thermosphere model, self-consistent wave–particle interaction simulations (electron hybrid code and ion hybrid code), the ionospheric electric potential (GEMSIS-POT) model, and SuperDARN electric field models with data assimilation. ERG (Arase) science center tools to support integrated studies with various kinds of data are also briefly introduced.

  18. Magnetic fluctuations embedded in dipolarization inside geosynchronous orbit and their associated selective acceleration of O<sup>+</sup> ions

    Nosé M., Takahashi K., Keika K., Kistler L.M., Koga K., Koshiishi H., Matsumoto H., Shoji M., Miyashita Y., Nomura R.

    Journal of Geophysical Research: Space Physics   119 巻 ( 6 ) 頁: 4639 - 4655   2014年6月

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    記述言語:日本語   掲載種別:研究論文(学術雑誌)   出版者・発行元:Journal of Geophysical Research: Space Physics  

    We study magnetic fluctuations embedded in dipolarizations in the inner magnetosphere (a geocentric distance of ≤6.6 RE) and their associated ion flux changes, using the Engineering Test Satellite VIII and Active Magnetospheric Particle Tracer Explorers/CCE satellites. We select seven events of dipolarization that occur during the main phase of magnetic storms having a minimum value of the Dst index less than -40 nT. It is found that (1) all of the dipolarization events are accompanied by strong magnetic fluctuations with the major frequency close to the local O+ gyrofrequency; (2) the magnetic fluctuations appear with significant amplitude in the component nearly parallel to the local magnetic field; (3) the strong flux enhancement is seen in the energy range of 1-10 keV only for O+ ions. In terms of frequency and dominant components of the magnetic fluctuations, they are considered to be excited by the drift-driven electromagnetic ion cyclotron (EMIC) instability that is recently identified with the linear theory. We perform particle tracing for H+ and O+ ions in the electromagnetic fields modeled by the linear dispersion relation of the drift-driven EMIC instability. Results show that the O+ ions are accelerated to the energy range of 0.5-5 keV and undergo a significant modification of the spectral shape, while the H+ ions have no clear change of spectral shape, being consistent with the observations. We therefore suggest that the electromagnetic fluctuations associated with the dipolarizations can accelerate O+ ions locally and nonadiabatically in the inner magnetosphere. This selective acceleration of O+ ions may play a role in enhancing the O+ energy density in the storm time ring current. ©2014. American Geophysical Union. All Rights Reserved.

    DOI: 10.1002/2014JA019806

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  19. Electromagnetic ion cyclotron rising tone emissions observed by THEMIS probes outside the plasmapause

    Satoko Nakamura, Yoshiharu Omura, Shinobu Machida, Masafumi Shoji, Masahito Nosé, Vassilis Angelopoulos

    Journal of Geophysical Research: Space Physics   119 巻 ( 3 ) 頁: 1874 - 1886   2014年3月

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    記述言語:英語   掲載種別:研究論文(学術雑誌)   出版者・発行元:American Geophysical Union (AGU)  

    We report observations of electromagnetic ion cyclotron (EMIC) triggered emissions observed by the Time History of Events and Macroscale Interactions during Substorms (THEMIS) probes outside the plasmasphere. Although these phenomena have recently received much attention because of the possibility of strong interaction with particles, only a few events of EMIC triggered emissions have been reported near the equatorial plasmapause. We performed a survey of the THEMIS probe data and found various types of emissions mainly on the dayside at radial distances of 6-10 RE. We study three distinctive events in detail. The first is a typical event with an obvious rising tone emission in the afternoon sector. The emissions in the second event are simultaneously excited in different frequency bands separated by the cyclotron frequency of helium ions. In the third event, which occurred near local noon, rising tone emissions were excited in an extended region near the equator where the field-aligned B gradient was much reduced because of compression of the magnetosphere by the solar wind. We compare these events with the nonlinear wave growth theory developed by Omura et al. (2010). In all events, it is found that the observed relationship between the amplitudes and frequencies of the emissions are in good agreement with the theory. Key Points Tens of EMIC emissions were observed by THEMIS outside the plasmasphere Most emissions consist of coherent rising tones from the equatorial region The characteristics are in agreement with the nonlinear wave growth theory ©2014. American Geophysical Union. All Rights Reserved.

    DOI: 10.1002/2013ja019146

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    CiNii Research

  20. 専門知のための科学データ融合表示ツール

    村田 健史, 鵜川 健太郎, 村永 和哉, 鈴木 豊, 渡邉 英伸, 是津 耕司, 北本 朝展, 篠原 育, 笠原 禎也, 能勢 正仁, 岡田 雅樹, 小嶋 浩嗣, 山本 和憲

    情報知識学会誌   24 巻 ( 2 ) 頁: 118 - 124   2014年

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    記述言語:日本語   掲載種別:研究論文(学術雑誌)   出版者・発行元:情報知識学会  

    本稿では,Web2.0で提案された集合知の概念を学術分野に拡張し,専門知・学術知を提案する.集合知ではインターネット上で一般市民からの情報を収集することで新しい情報を構築するのに対 し,専門知では異なる学術研究情報を融合し,一般社会に向けて情報を発信する.専門知においては,どのような情報をどのように集約し,提示するかが肝要となる.本研究では収集した科学データを融合して表示するための科学データ融合表示ツールを開発した.

    DOI: 10.2964/jsik_2014_007

    CiNii Research

  21. A statistical study of energy release and transport midway between the magnetic reconnection and initial dipolarization regions in the near-Earth magnetotail associated with substorm expansion onsets

    Miyashita Y., Machida S., Nose M., Liou K., Saito Y., Paterson W. R.

    JOURNAL OF GEOPHYSICAL RESEARCH-SPACE PHYSICS   117 巻 ( 11 )   2012年11月

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    記述言語:日本語   掲載種別:研究論文(学術雑誌)   出版者・発行元:Journal of Geophysical Research: Space Physics  

    Our previous study showed that the energy release associated with substorm expansion onsets is the most significant midway between the magnetic reconnection and initial dipolarization regions (-12 > X >-18 R E in the premidnight sector) in the magnetotail. In the present paper, we have statistically studied the substorm-associated energy balance and transport in the magnetotail, focusing on the midway region as well as the near-Earth initial dipolarization region (X > ∼-12 RE). We find that a large amount of energy is released in the midway region, associated with onsets, but only a part of this energy is transported to the near-Earth initial dipolarization region mainly in the form of the thermal flux and the wave Poynting flux. It is possible that the energy carried by fast earthward flows and waves from the reconnection region is not sufficient for the thermal energy increase and the outward transported energy in the initial dipolarization region, although the magnetic flux may be sufficiently carried. A considerably large amount of the magnetic energy comes from the lobes in the form of the Poynting flux also in the initial dipolarization region. © 2012. American Geophysical Union. All Rights Reserved.

    DOI: 10.1029/2012JA017925

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  22. Oxygen torus in the deep inner magnetosphere and its contribution to recurrent process of O+-rich ring current formation

    Nose M., Takahashi K., Anderson R. R., Singer H. J.

    JOURNAL OF GEOPHYSICAL RESEARCH-SPACE PHYSICS   116 巻 ( 10 )   2011年10月

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    記述言語:日本語   掲載種別:研究論文(学術雑誌)  

    DOI: 10.1029/2011JA016651

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  23. Energetic O+ and H+ ions in the plasma sheet: Implications for the transport of ionospheric ions

    Ohtani S., Nose M., Christon S. P., Lui A. T. Y.

    JOURNAL OF GEOPHYSICAL RESEARCH-SPACE PHYSICS   116 巻 ( 10 )   2011年10月

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    記述言語:日本語   掲載種別:研究論文(学術雑誌)  

    DOI: 10.1029/2011JA016532

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  24. Pi2 pulsations in the inner magnetosphere simultaneously observed by the Active Magnetospheric Particle Tracer Explorers/Charge Composition Explorer and Dynamics Explorer 1 satellites

    Teramoto M., Takahashi K., Nose M., Lee D. -H., Sutcliffe P. R.

    JOURNAL OF GEOPHYSICAL RESEARCH-SPACE PHYSICS   116 巻 ( 7 )   2011年7月

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    記述言語:日本語   掲載種別:研究論文(学術雑誌)  

    DOI: 10.1029/2010JA016199

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  25. Magnetic field depression at the Earth's surface during energetic neutral atom emission fade-out in the inner magnetosphere

    Nose M., Ohtani S., Brandt P. C. Son, Iyemori T., Keika K., Lee D. -Y.

    JOURNAL OF GEOPHYSICAL RESEARCH-SPACE PHYSICS   116 巻 ( 6 )   2011年6月

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    記述言語:日本語   掲載種別:研究論文(学術雑誌)  

    DOI: 10.1029/2010JA015799

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  26. Evolution of ring current ion energy spectra during the storm recovery phase: Implication for dominant ion loss processes

    Keika K., Brandt P. C., Nose M., Mitchell D. G.

    JOURNAL OF GEOPHYSICAL RESEARCH-SPACE PHYSICS   116 巻 ( 3 )   2011年3月

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    記述言語:日本語   掲載種別:研究論文(学術雑誌)  

    DOI: 10.1029/2010JA015628

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  27. Modeling the superstorm in November 2003

    Fok Mei-Ching, Moore Thomas E., Slinker Steve P., Fedder Joel A., Delcourt Dominique C., Nose Masahito, Chen Sheng-Hsien

    JOURNAL OF GEOPHYSICAL RESEARCH-SPACE PHYSICS   116 巻 ( 1 )   2011年1月

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    記述言語:日本語   掲載種別:研究論文(学術雑誌)  

    DOI: 10.1029/2010JA015720

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  28. Multipoint observation of fast mode waves trapped in the dayside plasmasphere

    Takahashi Kazue, Bonnell John, Glassmeier Karl-Heinz, Angelopoulos Vassilis, Singer Howard J., Chi Peter J., Denton Richard E., Nishimura Yukitoshi, Lee Dong-Hun, Nose Masahito, Liu Wenlong

    JOURNAL OF GEOPHYSICAL RESEARCH-SPACE PHYSICS   115 巻 ( 12 )   2010年12月

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    記述言語:日本語   掲載種別:研究論文(学術雑誌)  

    DOI: 10.1029/2010JA015956

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  29. Pressure changes associated with substorm depolarization in the near-Earth plasma sheet

    Miyashita Y., Machida S., Ieda A., Nagata D., Kamide Y., Nose M., Liou K., Mukai T., Christon S. P., Russell C. T., Shinohara I., Saito Y.

    JOURNAL OF GEOPHYSICAL RESEARCH-SPACE PHYSICS   115 巻 ( 12 )   2010年12月

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    記述言語:日本語   掲載種別:研究論文(学術雑誌)   出版者・発行元:Journal of Geophysical Research: Space Physics  

    We have studied plasma (ion) pressure changes that occurred in association with the dipolarization in the near-Earth plasma sheet around substorm onsets. Using Geotail data, we have performed a superposed epoch analysis in addition to detailed examinations of two individual cases with special emphasis on the contribution of high-energy particles to the plasma pressure. It is found that, unlike previously reported results, the plasma pressure does increase in association with the initial dipolarization at X > ∼-12 RE and -2 < Y < 6 RE, with the increase largely due to high-energy particles. Outside the initial dipolarization region, particularly tailward and duskward of this region, the plasma pressure begins to decrease owing to the magnetic reconnection before onset or before the dipolarization region reaches there. At later times, the plasma pressure tends to increase there, related to the expanding dipolarization region, but the contribution of high-energy particles is not very large. These observations suggest the following. The rarefaction wave scenario proposed in the current disruption model is questionable. The radial and azimuthal pressure gradients may strengthen between the initial dipolarization and outside regions, possibly resulting in stronger braking of fast earthward flows and changes in field-aligned currents. The characteristics of the dipolarization may differ between the initial dipolarization and tailward regions, which would be possibly reflected in the auroral features. Furthermore, we have examined the specific entropy and the ion β. The specific entropy increases in the plasma sheet in the dipolarization region as well as in the midtail region in conjunction with substorm onsets, suggesting from the ideal MHD point of view that the substorm processes are nonadiabatic. The ion β is found to peak at the magnetic equator in the initial dipolarization region around dipolarization onsets. Copyright 2010 by the American Geophysical Union.

    DOI: 10.1029/2010JA015608

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  30. Magnetic field dipolarization in the deep inner magnetosphere and its role in development of O+-rich ring current

    Nose M., Koshiishi H., Matsumoto H., Brandt P. Cson, Keika K., Koga K., Goka T., Obara T.

    JOURNAL OF GEOPHYSICAL RESEARCH-SPACE PHYSICS   115 巻 ( 9 )   2010年9月

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    記述言語:日本語   掲載種別:研究論文(学術雑誌)  

    DOI: 10.1029/2010JA015321

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  31. A new generation mechanism of butterfly pitch angle distributions of energetic ions: Multiple pitch angle scattering in the stretched magnetic field

    Shibahara K., Nose M., Fritz T. A., Niehof J.

    JOURNAL OF GEOPHYSICAL RESEARCH-SPACE PHYSICS   115 巻 ( 7 )   2010年7月

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    記述言語:日本語   掲載種別:研究論文(学術雑誌)  

    DOI: 10.1029/2010JA015281

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  32. The role of magnetic field fluctuations in nonadiabatic acceleration of ions during dipolarization

    Ono Y., Nose M., Christon S. P., Lui A. T. Y.

    JOURNAL OF GEOPHYSICAL RESEARCH-SPACE PHYSICS   114 巻 ( 5 )   2009年5月

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    記述言語:日本語   掲載種別:研究論文(学術雑誌)  

    DOI: 10.1029/2008JA013918

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  33. A state-of-the-art picture of substorm-associated evolution of the near-Earth magnetotail obtained from superposed epoch analysis

    Miyashita Y., Machida S., Kamide Y., Nagata D., Liou K., Fujimoto M., Ieda A., Saito M. H., Russell C. T., Christon S. P., Nose M., Frey H. U., Shinohara I., Mukai T., Saito Y., Hayakawa H.

    JOURNAL OF GEOPHYSICAL RESEARCH-SPACE PHYSICS   114 巻 ( 1 )   2009年1月

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    記述言語:日本語   掲載種別:研究論文(学術雑誌)   出版者・発行元:Journal of Geophysical Research: Space Physics  

    We have obtained a state-of-the-art picture of substorm-associated evolution of the near-Earth magnetotail and the inner magnetosphere for understanding the substorm triggering mechanism. We performed superposed epoch analysis of Geotail, Polar, and GOES data with 2-min resolution, utilizing a total of 3787 substorms for each of which auroral breakup was determined from Polar UVI or IMAGE FUV auroral imager data. The decrease of the north-south magnetic field associated with plasmoids and the initial total pressure decrease suggest that the magnetic reconnection first occurs in the premidnight tail, on average, at X ∼ -16 to -20 RE at least 2 min before auroral onset. The magnetic reconnection site is located near the tailward edge of a region of considerably taillike magnetic field lines and intense cross-tail current, which extends from X ∼ -5 to -20 RE in the premidnight sector. Then the plasmoid substantially evolves tailward of X ∼ -20 R E immediately after onset. Almost simultaneously with the magnetic reconnection, the dipolarization begins first at X ∼ -7 to -10 RE 2 min before onset. The dipolarization region then expands tailward as well as in the dawn-dusk directions and earthward. We find that the total pressure generally enhances in association with the dipolarization, with the contribution of high-energy particles. Also, energy release is more significant between the regions of the magnetic reconnection and the initial dipolarization. The present results will be helpful as a reference guide to developing the overall picture of magnetotail evolution and studying the causal relationship between the magnetic reconnection and the dipolarization as well as detailed mechanisms of each of the two processes on the basis of multispacecraft observations. Copyright 2009 by the American Geophysical Union.

    DOI: 10.1029/2008JA013225

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  34. Geotail observations of plasma sheet ion composition over 16 years: On variations of average plasma ion mass and O<sup>+</sup> triggering substorm model

    Nosé M., Ieda A., Christon S.P.

    Journal of Geophysical Research: Space Physics   114 巻 ( 7 )   2009年

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    記述言語:日本語   掲載種別:研究論文(学術雑誌)   出版者・発行元:Journal of Geophysical Research: Space Physics  

    We examined long-term variations of ion composition in the plasma sheet, using energetic (9.4-212.1 keV/e) ion flux data obtained by the suprathermal ion composition spectrometer (STICS) sensor of the energetic particle and ion composition (EPIC) instrument on board the Geotail spacecraft. EPIC/STICS observations are available from 17 October 1992 for more than 16 years, covering the declining phase of solar cycle 22, all of solar cycle 23, and the early phase of solar cycle 24. This unprecedented long-term data set revealed that (1) the He+/H+ and O+/H+ flux ratios in the plasma sheet were dependent on the F10.7 index; (2) the F10.7 index dependence is stronger for O+/H+ than He +/H+; (3) the O+/H+ flux ratio is also weakly correlated with the ∑Kp index; and (4) the He 2+/H+ flux ratio in the plasma sheet appeared to show no long-term trend. From these results, we derived empirical equations related to plasma sheet ion composition and the F10.7 index and estimated that the average plasma ion mass changes from ∼1.1 amu during solar minimum to ∼2.8 amu during solar maximum. In such a case, the Alfvén velocity during solar maximum decreases to ∼60% of the solar minimum value. Thus, physical processes in the plasma sheet are considered to be much different between solar minimum and solar maximum. We also compared long-term variation of the plasma sheet ion composition with that of the substorm occurrence rate, which is evaluated by the number of Pi2 pulsations. No correlation or negative correlation was found between them. This result contradicts the O+ triggering substorm model, in which heavy ions in the plasma sheet increase the growth rate of the linear ion tearing mode and play an important role in localization and initiation of substorms. In contrast, O+ ions in the plasma sheet may prevent occurrence of substorms. Copyright 2009 by the American Geophysical Union.

    DOI: 10.1029/2009JA014203

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  35. Statistical analysis of Pi2 pulsations inside and outside the plasmasphere observed by the polar orbiting DE-1 satellite

    Teramoto M., Nose M., Sutcliffe P. R.

    JOURNAL OF GEOPHYSICAL RESEARCH-SPACE PHYSICS   113 巻 ( A7 )   2008年7月

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    記述言語:日本語   掲載種別:研究論文(学術雑誌)  

    DOI: 10.1029/2007JA012740

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  36. Storm phase dependence of ion outflow: Statistical signatures obtained by IMAGE/LENA

    Kunori T., Nose M., Taguchi S., Hosokawa K., Collier M. R., Moore T. E.

    GEOPHYSICAL RESEARCH LETTERS   34 巻 ( 18 )   2007年9月

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    記述言語:日本語   掲載種別:研究論文(学術雑誌)  

    DOI: 10.1029/2007GL029877

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  37. Coupling of perturbations in the solar wind density to global Pi3 pulsations: A case study

    Han D.-S., Yang H.-G., Chen Z.-T., Araki T., Dunlop M. W., Nose M., Iyemori T., Li Q., Gao Y.-F., Yumoto K.

    JOURNAL OF GEOPHYSICAL RESEARCH-SPACE PHYSICS   112 巻 ( A5 )   2007年5月

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    記述言語:日本語   掲載種別:研究論文(学術雑誌)  

    DOI: 10.1029/2006JA011675

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  38. Polarization analysis of a Pi2 pulsation using continuous wavelet transform

    Kulesh M., Nose M., Holschneider A., Yumoto K.

    EARTH PLANETS AND SPACE   59 巻 ( 8 ) 頁: 961 - 970   2007年

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    記述言語:日本語   掲載種別:研究論文(学術雑誌)  

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  39. Contribution of charge exchange loss to the storm time ring current decay: IMAGE/HENA observations

    Keika K., Nose M., Brandt P. C., Ohtani S., Mitchell D. G., Roelof E. C.

    JOURNAL OF GEOPHYSICAL RESEARCH-SPACE PHYSICS   111 巻 ( A11 )   2006年11月

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    記述言語:日本語   掲載種別:研究論文(学術雑誌)  

    DOI: 10.1029/2006JA011789

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  40. Longitudinal dependence of characteristics of low-latitude Pi2 pulsations observed at Kakioka and Hermanus

    Nose M., Liou K., Sutcliffe P. R.

    EARTH PLANETS AND SPACE   58 巻 ( 6 ) 頁: 775 - 783   2006年

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    記述言語:日本語   掲載種別:研究論文(学術雑誌)  

    Web of Science

  41. Geomagnetic pulsations caused by the Sumatra earthquake on December 26, 2004

    Iyemori T, Nose M, Han DS, Gao YF, Hashizume M, Choosakul N, Shinagawa H, Tanaka Y, Utsugi M, Saito A, McCreadie H, Odagi Y, Yang FX

    GEOPHYSICAL RESEARCH LETTERS   32 巻 ( 20 ) 頁: 1 - 4   2005年10月

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    記述言語:日本語   掲載種別:研究論文(学術雑誌)  

    DOI: 10.1029/2005GL024083

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  42. Outflow of energetic ions from the magnetosphere and its contribution to the decay of the storm time ring current

    Keika K, Nose M, Ohtani S, Takahashi K, Christon SP, McEntire RW

    JOURNAL OF GEOPHYSICAL RESEARCH-SPACE PHYSICS   110 巻 ( A9 )   2005年9月

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    記述言語:日本語   掲載種別:研究論文(学術雑誌)  

    DOI: 10.1029/2004JA010970

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  43. Overwhelming O+ contribution to the plasma sheet energy density during the October 2003 superstorm: Geotail/EPIC and IMAGE/LENA observations

    Nose M, Taguchi S, Hosokawa K, Christon SP, McEntire RW, Moore TE, Collier MR

    JOURNAL OF GEOPHYSICAL RESEARCH-SPACE PHYSICS   110 巻 ( A9 )   2005年8月

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    記述言語:日本語   掲載種別:研究論文(学術雑誌)  

    DOI: 10.1029/2004JA010930

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  44. Storm-substorm relationship: Variations of the hydrogen and oxygen energetic neutral atom intensities during storm-time substorms

    Ohtani S, Brandt PC, Mitchell DG, Singer H, Nose M, Reeves GD, Mende SB

    JOURNAL OF GEOPHYSICAL RESEARCH-SPACE PHYSICS   110 巻 ( A7 )   2005年7月

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    記述言語:日本語   掲載種別:研究論文(学術雑誌)  

    DOI: 10.1029/2004JA010954

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  45. Comparison of energetic ion composition between ring current and plasma sheet

    Nose M, McEntire RW, Christon SP

    Frontiers in Magnetospheric Plasma Physics: Celebrating 10 Years of Geotail Operation     頁: 198 - 202   2005年

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    記述言語:日本語   掲載種別:研究論文(学術雑誌)  

    Web of Science

  46. Influence of solar wind on source of ring current plasma

    Nose M, McEntire RW, Christon SP

    Frontiers in Magnetospheric Plasma Physics: Celebrating 10 Years of Geotail Operation     頁: 48 - 53   2005年

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    記述言語:日本語   掲載種別:研究論文(学術雑誌)  

    Web of Science

  47. Geomagnetic activity dependence of occurrence probability and spatial distribution of upstream events

    Keika K, Nose M, Christon SP, McEntire RW

    Frontiers in Magnetospheric Plasma Physics: Celebrating 10 Years of Geotail Operation     頁: 297 - 300   2005年

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    記述言語:日本語   掲載種別:研究論文(学術雑誌)  

    Web of Science

  48. Multipoint observations of a Pi2 pulsation on morningside: The 20 September 1995 event

    Nose M, Takahashi K, Uozumi T, Yumoto K, Miyoshi Y, Morioka A, Milling DK, Sutcliffe PR, Matsumoto H, Goka T, Nakata H

    JOURNAL OF GEOPHYSICAL RESEARCH-SPACE PHYSICS   108 巻 ( A5 )   2003年5月

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    記述言語:日本語   掲載種別:研究論文(学術雑誌)  

    DOI: 10.1029/2002JA009747

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  49. CRRES electric field study of the radial mode structure of Pi2 pulsations

    Takahashi K, Lee DH, Nose M, Anderson RR, Hughes WJ

    JOURNAL OF GEOPHYSICAL RESEARCH-SPACE PHYSICS   108 巻 ( A5 )   2003年5月

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    記述言語:日本語   掲載種別:研究論文(学術雑誌)  

    DOI: 10.1029/2002JA009761

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  50. Local time dependence of the frequency of Pi2 waves simultaneously observed at 5 low-latitude stations

    Han DS, Iyemori T, Gao YF, Sano YH, Yang FX, Li WS, Nose M

    EARTH PLANETS AND SPACE   55 巻 ( 10 ) 頁: 601 - 612   2003年

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    記述言語:日本語   掲載種別:研究論文(学術雑誌)  

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  51. Quiet time magnetotail dynamics and their implications for the substorm trigger

    Ohtani S, Yamaguchi R, Nose M, Kawano H, Engebretson M, Yumoto K

    JOURNAL OF GEOPHYSICAL RESEARCH-SPACE PHYSICS   107 巻 ( A2 )   2002年2月

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    記述言語:日本語   掲載種別:研究論文(学術雑誌)  

    DOI: 10.1029/2001JA000116

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  52. Local time dependence of the dominant frequency of Pi2 pulsations at mid- and low-latitudes

    Kosaka K, Iyemori T, Nose M, Bitterly M, Bitterly J

    EARTH PLANETS AND SPACE   54 巻 ( 7 ) 頁: 771 - 781   2002年

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    記述言語:日本語   掲載種別:研究論文(学術雑誌)  

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  53. Storm-substorm relationship: Contribution of the tail current to Dst

    Ohtani S, Nose M, Rostoker G, Singer H, Lui ATY, Nakamura M

    JOURNAL OF GEOPHYSICAL RESEARCH-SPACE PHYSICS   106 巻 ( A10 ) 頁: 21199 - 21209   2001年10月

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    記述言語:日本語   掲載種別:研究論文(学術雑誌)  

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  54. Ion composition of the near-Earth plasma sheet in storm and quiet intervals: Geotail/EPIC measurements

    Nose M, Ohtani S, Takahashi K, Lui ATY, McEntire RW, Williams DJ, Christon SP, Yumoto K

    JOURNAL OF GEOPHYSICAL RESEARCH-SPACE PHYSICS   106 巻 ( A5 ) 頁: 8391 - 8403   2001年5月

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    記述言語:日本語   掲載種別:研究論文(学術雑誌)  

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  55. Composition of energetic neutral atoms during a storm main phase

    Lui ATY, McEntire RW, Nose M, Williams DJ

    GEOPHYSICAL RESEARCH LETTERS   28 巻 ( 7 ) 頁: 1363 - 1366   2001年4月

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    記述言語:日本語   掲載種別:研究論文(学術雑誌)  

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  56. Convection enhancements in the low-latitude lobe for substorm onset

    Taguchi S, Kiyohara M, Mukai T, Nose M, Saito Y

    JOURNAL OF GEOPHYSICAL RESEARCH-SPACE PHYSICS   106 巻 ( A3 ) 頁: 3943 - 3952   2001年3月

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    記述言語:日本語   掲載種別:研究論文(学術雑誌)  

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  57. Change of energetic ion composition in the plasma sheet during substorms

    Nose M, Ohtani S, Lui ATY, Christon SP, McEntire RW, Williams DJ, Mukai T, Saito Y, Yumoto K

    JOURNAL OF GEOPHYSICAL RESEARCH-SPACE PHYSICS   105 巻 ( A10 ) 頁: 23277 - 23286   2000年10月

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    記述言語:日本語   掲載種別:研究論文(学術雑誌)  

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  58. Acceleration of oxygen ions of ionospheric origin in the near-Earth magnetotail during substorms

    Nose M, Lui ATY, Ohtani S, Mauk BH, McEntire RW, Williams DJ, Mukai T, Yumoto K

    JOURNAL OF GEOPHYSICAL RESEARCH-SPACE PHYSICS   105 巻 ( A4 ) 頁: 7669 - 7677   2000年4月

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    記述言語:日本語   掲載種別:研究論文(学術雑誌)  

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  59. Near-Earth dipolarization: Evidence for a non-MHD process

    Lui A.T.Y., Liou K., Nosé M., Ohtani S., Williams D.J., Mukai T., Tsuruda K., Kokubun S.

    Geophysical Research Letters   26 巻 ( 19 ) 頁: 2905 - 2908   1999年10月

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    記述言語:日本語   掲載種別:研究論文(学術雑誌)   出版者・発行元:Geophysical Research Letters  

    We have investigated a near-Earth dipolarization event in the midnight sector using simultaneous observations of Polar and Geotail. We have found evidence for near-Earth dipolarization to be a non-MHD process: dipolarization occurring without significant plasma flow or with tailward flow and during dawnward electric field different from that inferred based on the frozen-in condition. These observations are inconsistent with the idea that dipolarization is an MHD process of magnetic flux pileup from braking of sunward plasma flow. Possible variances of the flow braking scenario are considered but none is satisfactory in accounting for the observed features. On the other hand, these findings are quite consistent with the expectations from the current disruption scenario.

    DOI: 10.1029/1999GL003620

    DOI: 10.1029/1999gl003620

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  60. Automated detection of Pi 2 pulsations using wavelet analysis: 2. An application for dayside Pi 2 pulsation study

    Nose M

    EARTH PLANETS AND SPACE   51 巻 ( 1 ) 頁: 23 - 32   1999年

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    記述言語:日本語   掲載種別:研究論文(学術雑誌)  

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  61. Geotail observations of north-south plasma velocity enhancements in the lobe near substorm expansion phase onset

    Taguchi S., Kiyohara M., Mukai T., Yamamoto T., Nose M., Saito Y., Kokubun S.

    Geophysical Research Letters   25 巻 ( 22 ) 頁: 4125 - 4128   1998年11月

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    記述言語:日本語   掲載種別:研究論文(学術雑誌)   出版者・発行元:Geophysical Research Letters  

    This paper reports on the enhancement of the lobe plasma velocity towards the neutral sheet. Analyzing the Geotail plasma and magnetic field data in the lobes earthward of X = -45 R(E), we identified 30 events of several-minute magnetic field increase-and-decrease during which the field tilts only southward; that is, the B(Z) variation is unipolar. For most of these events, we found that the lobe plasma velocity towards the neutral sheet is enhanced and peaked around the most southward tilting of the field. The average of the peak magnitude is about 130 km/s in a plane perpendicular to the magnetic field. For each case, this magnitude is roughly 1 - 10 % of the lobe Alfven speed. We interpret the velocity enhancement having these characteristics as signatures of the transition from plasma sheet reconnection to lobe reconnection at the near-Earth neutral line.

    DOI: 10.1029/1998GL900132

    DOI: 10.1029/1998gl900132

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  62. Temporal relationship between midtail traveling compression regions and substorm onset: Evidence for near-Earth neutral line formation in the late growth phase

    Taguchi S, Slavin JA, Kiyohara M, Nose M, Reeves GD, Lepping RP

    JOURNAL OF GEOPHYSICAL RESEARCH-SPACE PHYSICS   103 巻 ( A11 ) 頁: 26607 - 26612   1998年11月

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    記述言語:日本語   掲載種別:研究論文(学術雑誌)  

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  63. Electron precipitation accompanying Pc 5 pulsations observed by the DE satellites and at a ground station

    Nose M, Iyemori T, Sugiura M, Slavin JA, Hoffman RA, Winningham JD, Sato N

    JOURNAL OF GEOPHYSICAL RESEARCH-SPACE PHYSICS   103 巻 ( A8 ) 頁: 17587 - 17604   1998年8月

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    記述言語:日本語   掲載種別:研究論文(学術雑誌)  

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  64. Storm-time magnetic field variations observed by the ETS-VI satellite

    Terada N, Iyemori T, Nose M, Nagai T, Matsumoto H, Goka T

    EARTH PLANETS AND SPACE   50 巻 ( 10 ) 頁: 853 - 864   1998年

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    記述言語:日本語   掲載種別:研究論文(学術雑誌)  

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  65. Automated detection of Pi 2 pulsations using wavelet analysis: 1. Method and an application for substorm monitoring

    Nose M, Iyemori T, Takeda M, Kamei T, Milling DK, Orr D, Singer HJ, Worthington EW, Sumitomo N

    EARTH PLANETS AND SPACE   50 巻 ( 9 ) 頁: 773 - 783   1998年

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    記述言語:日本語   掲載種別:研究論文(学術雑誌)  

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  66. ULF pulsations observed by the ETS-VI satellite: Substorm associated azimuthal Pc 4 pulsations on the nightside

    Nose M, Iyemori T, Nakabe S, Nagai T, Matsumoto H, Goka T

    EARTH PLANETS AND SPACE   50 巻 ( 1 ) 頁: 63 - 80   1998年

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    記述言語:日本語   掲載種別:研究論文(学術雑誌)  

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  67. ETS-VI Magnetic Field Observations of the Near-Earth Magnetotail during Substorms

    Nagai T., Ondoh T., Matsumoto H., Goka T., Fukuda T., Nosé M., Iyemori T., Takahashi K., Kokubun S.

    Journal of Geomagnetism and Geoelectricity   48 巻 ( 42496 ) 頁: 741 - 748   1996年

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    記述言語:日本語   掲載種別:研究論文(学術雑誌)   出版者・発行元:Journal of Geomagnetism and Geoelectricity  

    The magnetic field experiment on board ETS-VI (the Engineering Test Satellite-VI) and initial results from the experiment are presented. ETS-VI was launched on August 28, 1994 and has been placed in anear equatorial orbit with a pcrigee of 2.3Re, an apogee of 7.1 Rc, an inclination of 13.4°, and an orbital period of 14.4 hours. The spacecraft is three-axis stabilized. The magnetic field experiment on board the satellite consists of a triaxial fluxgate magnetometer. The magnetometer has a sampling interval of 3 s, and except near perigee, it is operated in the mode having a ±256 nT dynamic range and a 0.125 nT resolution. We have examined the magnetometer data obtained at radial distances from 5.0 to 7.1Re, magnetic latitudes from-10° to 25°, and local times from 14 MLT through midnight to 04 MLT, to study magnetic field variations associated with substorms. Substorm-associated field variations are easily seen at larger radial distances and at local times later than 19 MLT. Using 92 substorm events that occurred in the 21-01 MLT sector, we have constructed the average field configuration during the growth phase. The magnetic field becomes highly taillike and its intensity increases at high latitudes (>10°), while the field intensity decreases at lower latitudes (<10°). The field configuration suggests that the inner edge of the growth phase current system is located near the synchronous altitude at the end of the growth phase. © 1996, Society of Geomagnetism and Earth, Planetary and Space Sciences. All rights reserved.

    DOI: 10.5636/jgg.48.741

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  68. ETS-VI magnetic field observations of the near-Earth magnetotail during substorms

    Nagai T., Ondoh T., Matsumoto H., Goka T., Fukuda T., Nosé M., Iyemori T., Takahashi K., Kokubun S.

    Earth, Planets and Space   48 巻 ( 5-6 ) 頁: 741 - 748   1996年

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    記述言語:日本語   掲載種別:研究論文(学術雑誌)   出版者・発行元:Earth, Planets and Space  

    The magnetic field experiment on board ETS-VI (the Engineering Test Satellite-VI) and initial results from the experiment are presented. ETS-VI was launched on August 28, 1994 and has been placed in a near equatorial orbit with a perigee of 2.3Re, an apogee of 7.1 Re, an inclination of 13.4°, and an orbital period of 14.4 hours. The spacecraft is three-axis stabilized. The magnetic field experiment on board the satellite consists of a triaxial fluxgate magnetometer. The magnetometer has a sampling interval of 3 s, and except near perigee, it is operated in the mode having a ±256 nT dynamic range and a 0.125 nT resolution. We have examined the magnetometer data obtained at radial distances from 5.0 to 7.1Re, magnetic latitudes from -10° to 25°, and local times from 14 MLT through midnight to 04 MLT, to study magnetic field variations associated with substorms. Substorm-associated field variations are easily seen at larger radial distances and at local times later than 19 MLT. Using 92 substorm events that occurred in the 21-01 MLT sector, we have constructed the average field configuration during the growth phase. The magnetic field becomes highly taillike and its intensity increases at high latitudes (>10°), while the field intensity decreases at lower latitudes (<10°). The field configuration suggests that the inner edge of the growth phase current system is located near the synchronous altitude at the end of the growth phase.

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  69. A STRONG DAWN DUSK ASYMMETRY IN PC5 PULSATION OCCURRENCE OBSERVED BY THE DE-1 SATELLITE

    NOSE M, IYEMORI T, SUGIURA M, SLAVIN JA

    GEOPHYSICAL RESEARCH LETTERS   22 巻 ( 15 ) 頁: 2053 - 2056   1995年8月

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    記述言語:日本語   掲載種別:研究論文(学術雑誌)  

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  70. Field-Aligned Low-Energy O+ Flux Enhancements in the Inner Magnetosphere Observed by Arase

    Nose M., Matsuoka A., Miyoshi Y., Asamura K., Hori T., Teramoto M., Shinohara I, Hirahara M.

    JOURNAL OF GEOPHYSICAL RESEARCH-SPACE PHYSICS   126 巻 ( 8 )   2021年8月

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    記述言語:日本語   掲載種別:研究論文(学術雑誌)   出版者・発行元:Journal of Geophysical Research: Space Physics  

    The present study examines the low-energy ion flux variations observed by the Arase satellite in the inner magnetosphere. From the magnetic field and ion flux data obtained by the fluxgate magnetometer and the low-energy particle experiments–ion mass analyzer onboard Arase, we find 55 events of the low-energy O+ flux enhancement accompanied with magnetic field dipolarization in the periods of April 1–October 31, 2017 and July 1, 2018–January 31, 2019. The low-energy O+ flux enhancements (a) start a few minutes after the dipolarization onset, (b) have energy-dispersed signatures with decreasing energy from a few keV down to ∼10 eV, (c) are observed in both storm and non-storm periods, (d) have a field-aligned distribution (α ∼ 0° in the southern hemisphere and α ∼ 180° in the northern hemisphere), (e) are accompanied by the low-energy H+ flux enhancements that have lower energies than O+ by a factor of 3–10, and (f) increase the O+ density and the O+/H+ density ratio by ∼10 times and 4–5 times, respectively. We perform a numerical simulation to trace ion trajectories forward in time from the Arase positions. It is revealed that both H+ and O+ ions drift eastward and reach the dawn-to-morning sector without being lost in the ionosphere, if the pitch angle scattering effect is considered near the equatorial plane. This result suggests that these low-energy field-aligned ions can contribute to formation of the warm plasma cloak.

    DOI: 10.1029/2021JA029168

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  71. Signal and Noise Separation From Satellite Magnetic Field Data Through Independent Component Analysis: Prospect of Magnetic Measurements Without Boom and Noise Source Information

    Imajo S., Nose M., Aida M., Matsumoto H., Higashio N., Tokunaga T., Matsuoka A.

    JOURNAL OF GEOPHYSICAL RESEARCH-SPACE PHYSICS   126 巻 ( 5 )   2021年5月

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    記述言語:日本語   掲載種別:研究論文(学術雑誌)   出版者・発行元:Journal of Geophysical Research: Space Physics  

    We propose an application of the independent component analysis (ICA) to separate satellite-induced time-varying stray fields from magnetic field data obtained using onboard multiple magnetometers. The ICA is a method for estimating source signals at multiple sites so that the estimated source signals can become statistically independent of each other. Since stray field variations are statistically independent of external natural field variations, the ICA method is expected to separate the natural variations from stray fields. Thus, we applied the ICA to magnetic field data from the first Quasi-Zenith Satellite, which has two triaxial fluxgate magnetometers, without using an extendable boom. First, we removed the long-period trend from the original data to create detrended data. Then, we applied the FastICA algorithm to the detrended data and obtained six independent components (ICs). The stray fields were successfully separated into three ICs (noise ICs), and the natural signals were represented by the other three ICs (signal ICs). Finally, we restored the observed signals from the signal ICs, and confirmed that the natural phenomena variations were not altered by the processing step. We also proposed a selection method of the noise ICs using the C coefficient, which is the coefficient of the variance of the mixing vectors. There was a large difference in C between the ICs whose C coefficients are the largest third and fourth ones. Overall, these results demonstrate the possibility that the ICA method can support for boom-less magnetic observations in future satellite missions.

    DOI: 10.1029/2020JA028790

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    その他リンク: https://onlinelibrary.wiley.com/doi/full-xml/10.1029/2020JA028790

  72. Magnetic Conjugacy of Pc1 Waves and Isolated Proton Precipitation at Subauroral Latitudes: Importance of Ionosphere as Intensity Modulation Region

    Ozaki Mitsunori, Shiokawa Kazuo, Horne Richard B., Engebretson Mark J., Lessard Marc, Ogawa Yasunobu, Hosokawa Keisuke, Nose Masahito, Ebihara Yusuke, Kadokura Akira, Yagitani Satoshi, Miyoshi Yoshizumi, Hashimoto Shion, Sinha Shipra, Sinha Ashwini K., Seemala Gopi K., Jun Chae-Woo

    GEOPHYSICAL RESEARCH LETTERS   48 巻 ( 5 )   2021年3月

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    記述言語:日本語   掲載種別:研究論文(学術雑誌)   出版者・発行元:Geophysical Research Letters  

    Pc1 geomagnetic pulsations, equivalent to electromagnetic ion cyclotron waves in the magnetosphere, display a specific amplitude modulation, though the region of the modulation remains an open issue. To classify whether the amplitude modulation has a magnetospheric or ionospheric origin, an isolated proton aurora (IPA), which is a proxy of Pc1 wave-particle interactions, is compared with the associated Pc1 waves for a geomagnetic conjugate pair, Halley Research Base in Antarctica and Nain in Canada. The temporal variation of an IPA shows a higher correlation coefficient (0.88) with Pc1 waves in the same hemisphere than that in the opposite hemisphere. This conjugate observation reveals that the classic cyclotron resonance is insufficient to determine the amplitude modulation. We suggest that direct wave radiation from the ionospheric current by IPA should also contribute to the amplitude modulation.

    DOI: 10.1029/2020GL091384

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    その他リンク: https://onlinelibrary.wiley.com/doi/full-xml/10.1029/2020GL091384

  73. Evolution of field-aligned current in the meridional plane during substorm: multipoint observations from satellites and ground stations 査読有り

    Imajo S., Nosé M., Aida M., Higashio N., Matsumoto H., Kiyokazu K., Smith C., MacDowall R.J., Yoshikawa A.

    Earth, Planets and Space   72 巻 ( 1 )   2020年12月

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    記述言語:日本語   掲載種別:研究論文(学術雑誌)   出版者・発行元:Earth, Planets and Space  

    We report the propagation of substorm-associated magnetic fluctuations by multipoint magnetic observations from ground and space in the same meridional plane. The first Quasi-Zenith Satellite (QZS-1), which has a unique orbit of quasi-zenith orbit with an inclination of 41 ∘, an apogee of 7.1 RE radial distance, and an orbital period of 24 h, can stay for a long time in the near-earth magnetotail away from the magnetic equator. We examined a substorm event during 15:00–16:00 UT on July 09, 2013 when QZS-1 was located at 31 ∘ dipole latitude and 23.5 h dipole magnetic local time. The Engineering Test Satellite VIII (ETS-VIII), Time History of Events and Macroscale Interactions during Substorms D (THEMIS-D) at a radial distance of ∼ 10 RE, and THEMIS-E at a radial distance of ∼ 7 RE were located near the equator in the similar magnetic meridian. The dipolarization was first observed at THEMIS-D at 15:14:30 UT. Then, ∼ 1 min later, magnetic fluctuations were observed by ETS-VIII and THEMIS-E. At the same time, the magnetic bay and Pi2 pulsation were observed at low-latitude magnetic observatories and the Radiation Belt Storm Probes B satellite in the inner magnetosphere. We found that QZS-1 away from the equator observed a strong azimuthal magnetic field fluctuation with a long delay of 15 min from the first dipolarization at THEMIS-D near the equator. The speed of the poleward propagating magnetic fluctuation between the ionospheric footprints is calculated to be 310 [m / s] , which is consistent with a typical speed of auroral poleward expansion. A similar time delay of the onset of the negative bay was observed between the Tixie (AACGM MLAT = 66. 8 ∘) and Kotelny (AACGM MLAT = 71. 0 ∘) observatories near the ionospheric footprint of satellites. We suggest that the long delay time of the magnetic fluctuation at QZS-1 was associated with the crossing of field-aligned current during the poleward expansion of the substorm current system. The distribution of azimuthal magnetic field variations in the magnetosphere indicates that the east side downward current extended more west side in the higher latitude part of the current wedge.

    DOI: 10.1186/s40623-020-01182-6

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    その他リンク: http://link.springer.com/article/10.1186/s40623-020-01182-6/fulltext.html

  74. Oxygen torus and its coincidence with EMIC wave in the deep inner magnetosphere: Van Allen Probe B and Arase observations

    Nose M., Matsuoka A., Kumamoto A., Kasahara Y., Teramoto M., Kurita S., Goldstein J., Kistler L. M., Singh S., Gololobov A., Shiokawa K., Imajo S., Oimatsu S., Yamamoto K., Obana Y., Shoji M., Tsuchiya F., Shinonara I, Miyoshi Y., Kurth W. S., Kletzing C. A., Smith C. W., MacDowal R. J., Spence H., Reeves G. D.

    EARTH PLANETS AND SPACE   72 巻 ( 1 )   2020年8月

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    記述言語:日本語   掲載種別:研究論文(学術雑誌)   出版者・発行元:Earth, Planets and Space  

    We investigate the longitudinal structure of the oxygen torus in the inner magnetosphere for a specific event found on 12 September 2017, using simultaneous observations from the Van Allen Probe B and Arase satellites. It is found that Probe B observed a clear enhancement in the average plasma mass (M) up to 3–4 amu at L = 3.3–3.6 and magnetic local time (MLT) = 9.0 h. In the afternoon sector at MLT ~ 16.0 h, both Probe B and Arase found no clear enhancements in M. This result suggests that the oxygen torus does not extend over all MLT but is skewed toward the dawn. Since a similar result has been reported for another event of the oxygen torus in a previous study, a crescent-shaped torus or a pinched torus centered around dawn may be a general feature of the O+ density enhancement in the inner magnetosphere. We newly find that an electromagnetic ion cyclotron (EMIC) wave in the H+ band appeared coincidently with the oxygen torus. From the lower cutoff frequency of the EMIC wave, the ion composition of the oxygen torus is estimated to be 80.6% H+, 3.4% He+, and 16.0% O+. According to the linearized dispersion relation for EMIC waves, both He+ and O+ ions inhibit EMIC wave growth and the stabilizing effect is stronger for He+ than O+. Therefore, when the H+ fraction or M is constant, the denser O+ ions are naturally accompanied by the more tenuous He+ ions, resulting in a weaker stabilizing effect (i.e., larger growth rate). From the Probe B observations, we find that the growth rate becomes larger in the oxygen torus than in the adjacent regions in the plasma trough and the plasmasphere.[Figure not available: see fulltext.]

    DOI: 10.1186/s40623-020-01235-w

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    その他リンク: http://link.springer.com/article/10.1186/s40623-020-01235-w/fulltext.html

  75. Arase Observation of the Source Region of Auroral Arcs and Diffuse Auroras in the Inner Magnetosphere 査読有り

    Shiokawa K., Nose M., Imajo S., Tanaka Y. -M., Miyoshi Y., Hosokawa K., Connors M., Engebretson M., Kazama Y., Wang S. -Y., Tam S. W. Y., Chang Tzu-Fang, Wang Bo-Jhou, Asamura K., Kasahara S., Yokota S., Hori T., Keika K., Kasaba Y., Shoji M., Kasahara Y., Matsuoka A., Shinohara I.

    JOURNAL OF GEOPHYSICAL RESEARCH-SPACE PHYSICS   125 巻 ( 8 )   2020年8月

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    記述言語:日本語   掲載種別:研究論文(学術雑誌)   出版者・発行元:Journal of Geophysical Research: Space Physics  

    Auroral arcs and diffuse auroras are common phenomena at high latitudes, though characteristics of their source plasma and fields have not been well understood. We report the first observation of fields and particles including their pitch-angle distributions in the source region of auroral arcs and diffuse auroras, using data from the Arase satellite at L ~ 6.0–6.5. The auroral arcs appeared and expanded both poleward and equatorward at local midnight from ~0308 UT on 11 September 2018 at Nain (magnetic latitude: 66°), Canada, during the expansion phase of a substorm, while diffuse auroras covered the whole sky after 0348 UT. The top part of auroral arcs was characterized by purple/blue emissions. Bidirectional field-aligned electrons with structured energy-time spectra were observed in the source region of auroral arcs, while source electrons became isotropic and less structured in the diffuse auroral region afterwards. We suggest that structured bidirectional electrons at energies below a few keV were caused by upward field-aligned potential differences (upward electric field along geomagnetic field) reaching high altitudes (~30,000 km) above Arase. The bidirectional electrons above a few keV were probably caused by Fermi acceleration associated with the observed field dipolarization. Strong electric-field fluctuations and earthward Poynting flux were observed at the arc crossing and are probably also caused by the field dipolarization. The ions showed time-pitch-angle dispersion caused by mirror reflection. These results indicate a clear contrast between auroral arcs and diffuse auroras in terms of source plasma and fields and generation mechanisms of auroral arcs in the inner magnetosphere.

    DOI: 10.1029/2019JA027310

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  76. Selective Acceleration of O+ by Drift-Bounce Resonance in the Earth's Magnetosphere: MMS Observations

    Oimatsu S., Nose M., Le G., Fuselier S. A., Ergun R. E., Lindqvist P. -A., Sormakov D.

    JOURNAL OF GEOPHYSICAL RESEARCH-SPACE PHYSICS   125 巻 ( 2 )   2020年2月

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    掲載種別:研究論文(学術雑誌)  

    DOI: 10.1029/2019JA027686

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  77. Remote Detection of Drift Resonance Between Energetic Electrons and Ultralow Frequency Waves: Multisatellite Coordinated Observation by Arase and Van Allen Probes 査読有り

    M. Teramoto, T. Hori, S. Saito, Y. Miyoshi, S. Kurita, N. Higashio, A. Matsuoka, Y. Kasahara, Y. Kasaba, T. Takashima, R. Nomura, M. Nos{\'{e, A. Fujimoto, Y.-M. Tanaka, M. Shoji, Y. Tsugawa, M. Shinohara, I. Shinohara, J. B. Blake, J.F. Fennell, S.G. Claudepierre, D. L. Turner, C. A. Kletzing, D. Sormakov, O. Troshichev

    Geophysical Research Letters   46 巻 ( 21 ) 頁: 11642 - 11651   2019年11月

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    記述言語:日本語   掲載種別:研究論文(学術雑誌)   出版者・発行元:American Geophysical Union ({AGU})  

    We report the electron flux modulations without corresponding magnetic fluctuations from unique multipoint satellite observations of the Arase (Exploration of Energization and Radiation in Geospace) and the Van Allen Probe (Radiation Belt Storm Probe [RBSP])-B satellites. On 30 March 2017, both Arase and RBSP-B observed periodic fluctuations in the relativistic electron flux with energies ranging from 500 keV to 2 MeV when they were located near the magnetic equator in the morning and dusk local time sectors, respectively. Arase did not observe Pc5 pulsations, while they were observed by RBSP-B. The clear dispersion signature of the relativistic electron fluctuations observed by Arase indicates that the source region is limited to the postnoon to the dusk sector. This is confirmed by RBSP-B and ground-magnetometer observations, where Pc5 pulsations are observed to drift-resonate with relativistic electrons on the duskside. Thus, Arase observed the drift-resonance signatures “remotely,” whereas RBSP-B observed them “locally.”.

    DOI: 10.1029/2019GL084379

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  78. Locally Generated ULF Waves in the Martian Magnetosphere: MAVEN Observations

    Harada Y., Ruhunusiri S., Halekas J.S., Espley J., DiBraccio G.A., Mcfadden J.P., Mitchell D.L., Mazelle C., Collinson G., Brain D.A., Hara T., Nosé M., Oimatsu S., Yamamoto K., Jakosky B.M.

    Journal of Geophysical Research: Space Physics   124 巻 ( 11 ) 頁: 8707 - 8726   2019年11月

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    記述言語:日本語   掲載種別:研究論文(学術雑誌)   出版者・発行元:Journal of Geophysical Research: Space Physics  

    We investigate Martian ultralow frequency (ULF) electromagnetic waves generated by local plasma instabilities below the Martian bow shock. Recent Mars Atmosphere and Volatile EvolutioN (MAVEN) observations have shown that ULF waves generated upstream of the Martian bow shock can propagate down to the upper ionosphere, possibly facilitating heavy ion escape from Mars by heating the ionospheric plasma. In contrast to the upstream waves oscillating near the upstream proton cyclotron frequency, we identify narrow band ULF magnetic field fluctuations with frequencies near the local proton cyclotron frequency (fcp(local)) from MAVEN data. In addition to expected proton cyclotron waves locally generated in the magnetosheath, we newly identify compressional narrow band emissions near fcp(local) (and its harmonics for some cases) in the dayside upper ionosphere and in the nightside magnetotail. The dayside waves are preferentially observed for high solar extreme ultraviolet (EUV) conditions and are often associated with ring/shell-like, hot protons of magnetosheath origin in the presence of cold, dense ionospheric protons. The nightside waves exhibit distinct preference for high-solar-EUV, strong-solar-wind conditions, under which both warm and cold protons are enhanced. The observed properties of these compressional waves are generally consistent with a proton Bernstein mode instability driven by a positive perpendicular slope in proton velocity distribution functions. The excited waves can cause perpendicular heating of thermal protons, thereby transferring energy from precipitating hot protons to cold ionospheric protons.

    DOI: 10.1029/2019ja027312

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    その他リンク: https://onlinelibrary.wiley.com/doi/full-xml/10.1029/2019JA027312

  79. Direct comparison between magnetospheric plasma waves and polar mesosphere winter echoes in both hemispheres 査読有り 国際誌

    Tanaka, Y.-M, T. Nishiyama, A. Kadokura, M. Ozaki, K. Shiokawa, S. Oyama, M. Nosé, T. Nagatsuma, M. Tsutsumi, K. Nishimura, K. Sato, Y. Miyoshi, Y. Kasahara, A. Kumamoto, F. Tsuchiya, M. Hikishima, S. Matsuda, A. Matsuoka, M. Shinohara, A. Fujimoto, M. Teramoto, R. Nomura, R. Kataoka, A. Sessai Yukimatu

    J. Geophys. Res. (SPA)   124 巻 ( 11 ) 頁: 9626 - 9639   2019年10月

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    記述言語:英語   掲載種別:研究論文(学術雑誌)   出版者・発行元:AGU (Wiley)  

    We present the first and direct comparison between magnetospheric plasma waves and polar mesosphere winter echoes (PMWE) simultaneously observed by the conjugate observation with Arase satellite and high‐power atmospheric radars in both hemispheres, namely, the Program of the Antarctic Syowa Mesosphere, Stratosphere, and Troposphere/Incoherent Scatter Radar at Syowa Station (SYO; −69.00°S, 39.58°E), Antarctica, and the Middle Atmosphere Alomar Radar System at Andøya (AND; 69.30°N, 16.04°E), Norway. The PMWE were observed during 03–07 UT on 21 March 2017, just after the arrival of corotating interaction region in front of high‐speed solar wind stream. An isolated substorm occurred at 04 UT during this interval. Electromagnetic ion cyclotron (EMIC) waves and whistler mode chorus waves were simultaneously observed near the magnetic equator and showed similar temporal variations to that of the PMWE. These results indicate that chorus waves as well as EMIC waves are drivers of precipitation of energetic electrons, including relativistic electrons, which make PMWE detectable at 55‐ to 80‐km altitude. Cosmic noise absorption measured with a 38.2‐MHz imaging riometer and low‐altitude echoes at 55–70 km measured with an medium‐frequency radar at SYO also support the relativistic electron precipitation. We suggest a possible scenario in which the various phenomena observed in near‐Earth space, such as magnetospheric plasma waves (EMIC waves and chorus waves), pulsating auroras, cosmic noise absorption, and PMWE, can be explained by the interaction between the high‐speed solar wind containing corotating interaction regions and the magnetosphere.

    DOI: 10.1029/2019JA026891

  80. Meridional distribution of middle-energy protons and pressure-driven currents in the nightside inner magnetosphere: Arase observations, 査読有り

    S. Imajo, M. Nose, S. Kasahara, S. Yokota, A. Matsuoka, K. Keika, T. Hori, M. Teramoto, K. Yamamoto, S. Oimatsu, R. Nomura, A. Fujimoto, I. Shinohara, Y. Miyoshi

    Journal of Geophysical Research: Space Physics   124 巻 ( 7 ) 頁: 5719 - 5733   2019年7月

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    記述言語:英語   掲載種別:研究論文(学術雑誌)   出版者・発行元:Journal of Geophysical Research: Space Physics  

    We examined the average meridional distribution of middle-energy protons (10–180 keV) and pressure-driven currents in the nightside (20–04 hr magnetic local time) ring current region during moderately disturbed times using the Arase satellite's data. Because the Arase satellite has a large inclination orbit of 31°, it covers the magnetic latitude (MLAT) in the range of −40° to 40° and a radial distance of <6RE. We found that the plasma pressure decreased significantly with increasing MLAT. The plasma pressure on the same L* shell at 30° < MLAT < 40° was ∼10–60% of that at 0° < 4 MLAT < 10°, and the rate of decrease was larger on lower L* shells. The pressure anisotropy, derived as the perpendicular pressure divided by the parallel pressure minus 1, decreased with radial distance and showed a weak dependence on MLAT. The magnitude of the plasma beta at 30°<MLAT<40° was 1 or 2 orders smaller than that at 0°<MLAT<10°. The plasma pressure normalized by the value at 0°<MLAT<10° estimated from the magnetic strength and anisotropy was roughly consistent with the observed plasma pressure for L*=3.5–5.5. The azimuthal pressure-gradient current derived from the plasma pressure was distributed over MLAT∼0–20°, while the curvature current was limited within MLAT∼0–10°. We suggest that the latitudinal dependence should be taken into account in interpretations of plasma parameters in successive orbits during magnetic storms.

    DOI: 10.1029/2019JA026682

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  81. Response of the Ionosphere-Plasmasphere Coupling to the September 2017 Storm:What Erodes the Plasmasphere so Severley? 査読有り

    Obana Yuki, Maruyama Naomi, Shinbori Atsuki, Hashimoto Kumiko K., Fedrizzi Mariangel, Nose Masahito, Otsuka Yuichi, Nishitani Nozomu, Hori Tomoaki, Kumamoto Atsushi, Tsuchiya Fuminori, Matsuda Shoya, Matsuoka Ayako, Kasahara Yoshiya, Yoshikawa Akimasa, Miyoshi Yoshizumi, Shinohara Iku

    SPACE WEATHER-THE INTERNATIONAL JOURNAL OF RESEARCH AND APPLICATIONS   17 巻 ( 6 ) 頁: 861 - 876   2019年6月

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    記述言語:日本語   掲載種別:研究論文(学術雑誌)   出版者・発行元:Space Weather  

    We report an extreme erosion of the plasmasphere arising from the September 2017 storm. The cold electron density is identified from the upper limit frequency of upper hybrid resonance waves observed by the Plasma Wave Experiment instrument onboard the Exploration of energization and Radiation in Geospace/Arase satellite. The electron density profiles reveal that the plasmasphere was severely eroded during the recovery phase of the storm and the plasmapause was located at L = 1.6–1.7 at 23 UT 8 September 2017. This is the first report of deep erosion of the plasmasphere (LPP < 2) with the in situ observation of the electron density. The degree of the severity is much more than what is expected from the relatively moderate value of the SYM-H minimum (−146 nT). We attempt to find a possible explanation for the observed severe depletion by using both observational evidence and numerical simulations. Our results suggest that the middle latitude electric field had penetrated from the high-latitude storm time convection for several hours. Such an unusually long-lasting penetration event can cause this observed degree of severity.

    DOI: 10.1029/2019SW002168

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  82. DC component of spacecraft-origin magnetic field noise at the Arase/MGF sensor: (1) Evaluation with Tsyganenko 89 model 査読有り

    Yamamoto, K, S. Oimatsu, M. Nosé, A. Matsuoka, M. Teramoto, S. Imajo

    JAXA Research and Development Report   JAXA-RR-18-005E 巻   頁: 23 - 28   2019年3月

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    記述言語:英語   掲載種別:研究論文(大学,研究機関等紀要)  

    DOI: 10.20637/JAXA-RR-18-005E/0004

  83. DC component of spacecraft-origin magnetic field noise at the Arase/MGF sensor: (2) Evaluation with Tsyganenko-Sitnov 04 model 査読有り

    JAXA Research and Development Report   JAXA-RR-18-005E 巻   頁: 29 - 35   2019年3月

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    記述言語:英語   掲載種別:研究論文(大学,研究機関等紀要)  

    DOI: 10.20637/JAXA-RR-18-005E/0005

  84. The Space Physics Environment Data Analysis System (SPEDAS) 査読有り

    Angelopoulos, V, P. Cruce, A. Drozdov. E, W. Grimes, N. Hatzigeorgiu, D. A. King, D. Larson, J. W. Lewis, J. M. McTiernan, D. A. Roberts, C. L. Russell, T. Hori, Y. Kasahara, A. Kumamoto, A. Matsuoka, Y. Miyashita, Y. Miyoshi, I. Shinohara, M. Teramoto, J. B. Faden, A. J. Halford, M. McCarthy, R. M. Millan, J. G. Sample, D. M. Smith, L. A. Woodger, A. Masson, A. A. Narock, K. Asamura, T. F. Chang, C.-Y. Chiang, Y. Kazama, K. Keika, S. Matsuda, T. Segawa, K. Seki, M. Shoji, S. W, Y. Tam, N. Umemura, B.-J. Wang, S.-Y. Wang, R. Redmon, J. V. Rodriguez, H. J. Singer, J. Vandegriff, S. Abe, M. Nose, A. Shinbori, Y.-M. Tanaka, S. UeNo, L. Andersson, P. Dunn, C. Fowler, J. S. Halekas, T. Hara, Y. Harada, C. O. Lee, R. Lillis, D. L. Mitchell, M. R. Argall, K. Bromund, J. L. Burch, I. J. Cohen, M. Galloy, B. Giles, A. N. Jaynes, O. Le Contel, M. Oka, T. D. Phan, B. M. Walsh, J. Westlake, F. D. Wilder, S. D. Bale, R. Livi, M. Pulupa, P. Whittlesey, A. DeWolfe, B. Harter, E. Lucas, U. Auster, J. W. Bonnell, C. M. Cully, E. Donovan, R. E. Ergun, H. U. Frey, B. Jackel, A. Keiling, H. Korth, J. P. McFadden, Y. Nishimura, F. Plaschke, P. Robert, D. L. Turner, J. M. Weygand, R. M. Candey, R. C. Johnson, T. Kovalick, M. H. Liu, R. E. McGuire, A. Breneman, K. Kersten, P. Schroeder

    Space Sci. Rev.   215 巻 ( 9 )   2019年2月

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    記述言語:英語   掲載種別:研究論文(学術雑誌)   出版者・発行元:Space Science Reviews  

    With the advent of the Heliophysics/Geospace System Observatory (H/GSO), a complement of multi-spacecraft missions and ground-based observatories to study the space environment, data retrieval, analysis, and visualization of space physics data can be daunting. The Space Physics Environment Data Analysis System (SPEDAS), a grass-roots software development platform (www.spedas.org), is now officially supported by NASA Heliophysics as part of its data environment infrastructure. It serves more than a dozen space missions and ground observatories and can integrate the full complement of past and upcoming space physics missions with minimal resources, following clear, simple, and well-proven guidelines. Free, modular and configurable to the needs of individual missions, it works in both command-line (ideal for experienced users) and Graphical User Interface (GUI) mode (reducing the learning curve for first-time users). Both options have “crib-sheets,” user-command sequences in ASCII format that can facilitate record-and-repeat actions, especially for complex operations and plotting. Crib-sheets enhance scientific interactions, as users can move rapidly and accurately from exchanges of technical information on data processing to efficient discussions regarding data interpretation and science. SPEDAS can readily query and ingest all International Solar Terrestrial Physics (ISTP)-compatible products from the Space Physics Data Facility (SPDF), enabling access to a vast collection of historic and current mission data. The planned incorporation of Heliophysics Application Programmer’s Interface (HAPI) standards will facilitate data ingestion from distributed datasets that adhere to these standards. Although SPEDAS is currently Interactive Data Language (IDL)-based (and interfaces to Java-based tools such as Autoplot), efforts are under-way to expand it further to work with python (first as an interface tool and potentially even receiving an under-the-hood replacement). We review the SPEDAS development history, goals, and current implementation. We explain its “modes of use” with examples geared for users and outline its technical implementation and requirements with software developers in mind. We also describe SPEDAS personnel and software management, interfaces with other organizations, resources and support structure available to the community, and future development plans.

    DOI: 10.1007/s11214-018-0576-4

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  85. Visualization of rapid electron precipitation via chorus element wave-particle interactions. 査読有り

    Ozaki M, Miyoshi Y, Shiokawa K, Hosokawa K, Oyama SI, Kataoka R, Ebihara Y, Ogawa Y, Kasahara Y, Yagitani S, Kasaba Y, Kumamoto A, Tsuchiya F, Matsuda S, Katoh Y, Hikishima M, Kurita S, Otsuka Y, Moore RC, Tanaka Y, Nosé M, Nagatsuma T, Nishitani N, Kadokura A, Connors M, Inoue T, Matsuoka A, Shinohara I

    Nature communications   10 巻 ( 1 ) 頁: 257   2019年1月

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    記述言語:英語   掲載種別:研究論文(学術雑誌)   出版者・発行元:Nature Communications  

    Chorus waves, among the most intense electromagnetic emissions in the Earth’s magnetosphere, magnetized planets, and laboratory plasmas, play an important role in the acceleration and loss of energetic electrons in the plasma universe through resonant interactions with electrons. However, the spatial evolution of the electron resonant interactions with electromagnetic waves remains poorly understood owing to imaging difficulties. Here we provide a compelling visualization of chorus element wave–particle interactions in the Earth’s magnetosphere. Through in-situ measurements of chorus waveforms with the Arase satellite and transient auroral flashes from electron precipitation events as detected by 100-Hz video sampling from the ground, Earth’s aurora becomes a display for the resonant interactions. Our observations capture an asymmetric spatial development, correlated strongly with the amplitude variation of discrete chorus elements. This finding is not theoretically predicted but helps in understanding the rapid scattering processes of energetic electrons near the Earth and other magnetized planets.

    DOI: 10.1038/s41467-018-07996-z

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  86. Spatiotemporal development of pulsating auroral patch associated with discrete chorus elements: Arase and PWING observations

    Ozaki M., Shiokawa K., Miyoshi Y., Hosokawa K., Oyama S., Yagitani S., Kasahara Y., Kasaba Y., Matsuda S., Kataoka R., Ebihara Y., Ogawa Y., Otsuka Y., Kurita S., Moore R. C., Tanaka Y. -M., Nose M., Nagatsuma T., Connors M., Nishitani N., Hikishima M., Kumamoto A., Tsuchiya F., Kadokura A., Nishiyama T., Inoue T., Imamura K., Matsuoka A., Shinohara I.

    2019 URSI ASIA-PACIFIC RADIO SCIENCE CONFERENCE (AP-RASC)     頁: .   2019年

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    記述言語:英語   掲載種別:研究論文(学術雑誌)  

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  87. The ARASE (ERG) magnetic field investigation 査読有り

    Matsuoka A, Teramoto M, Nomura R, Nosé M, Fujimoto A, Tanaka Y, Shinohara M, Nagatsuma T, Shiokawa K, Obana Y, Miyoshi Y, Mita M, Takashima T, Shinohara I

    Earth, Planets and Space   70 巻 ( 1 )   2018年12月

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    記述言語:英語   掲載種別:研究論文(学術雑誌)   出版者・発行元:Earth, Planets and Space  

    © 2018, The Author(s). The fluxgate magnetometer for the Arase (ERG) spacecraft mission was built to investigate particle acceleration processes in the inner magnetosphere. Precise measurements of the field intensity and direction are essential in studying the motion of particles, the properties of waves interacting with the particles, and magnetic field variations induced by electric currents. By observing temporal field variations, we will more deeply understand magnetohydrodynamic and electromagnetic ion-cyclotron waves in the ultra-low-frequency range, which can cause production and loss of relativistic electrons and ring-current particles. The hardware and software designs of the Magnetic Field Experiment (MGF) were optimized to meet the requirements for studying these phenomena. The MGF makes measurements at a sampling rate of 256 vectors/s, and the data are averaged onboard to fit the telemetry budget. The magnetometer switches the dynamic range between ± 8000 and ± 60,000 nT, depending on the local magnetic field intensity. The experiment is calibrated by preflight tests and through analysis of in-orbit data. MGF data are edited into files with a common data file form

    DOI: 10.1186/s40623-018-0800-1

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  88. Ion Energies Dominating Energy Density in the Inner Magnetosphere: Spatial Distributions and Composition, Observed by Arase/MEP-i 査読有り

    Keika K., Kasahara S., Yokota S., Hoshino M., Seki K., Nosé M., Amano T., Miyoshi Y., Shinohara I.

    Geophysical Research Letters   45 巻 ( 22 ) 頁: 12,153 - 12,162   2018年11月

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    記述言語:日本語   掲載種別:研究論文(学術雑誌)   出版者・発行元:Geophysical Research Letters  

    We investigate the spatial distributions and composition of contributing energies, which we term an energy range that makes the dominant contribution to energy density, in the inner magnetosphere during the main phase of magnetic storms. We analyze data from the medium-energy particle experiments-ion mass analyzer (MEP-i) on board the Arase satellite during six magnetic storms in year 2017 with the SYM-H minimum smaller than −50 nT. The results show that the inner part (L ≤ 5) is dominated by relatively low-energy ions adiabatically transported from the plasma sheet by enhanced convection. The contributing energies are higher for O+ than for H+ at higher L shells (L > 5), particularly during the storms driven by coronal mass ejections. The results provide in situ evidence of the contribution from mass-dependent/selective acceleration processes associated with substorm activity to the buildup of the outer part the ring current.

    DOI: 10.1029/2018GL080047

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  89. Microscopic Observations of Pulsating Aurora Associated With Chorus Element Structures: Coordinated Arase Satellite-PWING Observations 査読有り

    Ozaki, M, K. Shiokawa, Y. Miyoshi, K. Hosokawa, S. Oyama, S. Yagitani, Y. Kasahara, Y. Kasaba, S. Matsuda, R. Kataoka, Y. Ebihara, Y. Ogawa, Y. Otsuka, S. kurita, R. C. Moore, Y. -M. Tanaka, M. Nose, T. Nagatsuma, M. Connors, N. Nishitani, Y. Katoh, M. Hikishima, A. Kumamoto, F. Tsuchiya, A. Kadokura, T. Nishiyama, T. Inoue, K. Imamura, A. Matsuoka, I. Shinohara

    Geophys. Res. Lett.   45 巻 ( 22 ) 頁: 12,125 - 12,134   2018年11月

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    記述言語:英語   掲載種別:研究論文(学術雑誌)   出版者・発行元:Geophysical Research Letters  

    Rapid (<1 s) intensity modulation of pulsating auroras is caused by successive chorus elements as a response to wave-particle interactions in the magnetosphere. Here we found that a pulsating auroral patch responds to the time spacing for successive chorus elements and possibly to chorus subpacket structures with a time scale of tens of milliseconds. These responses were identified from coordinated Arase satellite and ground (Gakona, Alaska) observations with a high-speed auroral imager (100 Hz). The temporal variations of auroral intensity in a few-hertz frequency range exhibited a spatial concentration at the lower-latitude edge of the auroral patch. The spatial evolution of the auroral patch showed repeated expansion/contraction with tens of kilometer scales in the ionosphere, which could be spatial behaviors in the wave-particle interactions. These observations indicate that chorus elements evolve coherently within the auroral patch, which is approximately 900 km in the radial and longitudinal directions at the magnetic equator.

    DOI: 10.1029/2018GL079812

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  90. Magnetosphere-ionosphere connection of storm-time Region-2 field-aligned current and ring current: Arase and AMPERE observations 査読有り

    Imajo S., Nosé M., Matsuoka A., Kasahara S., Yokota S., Teramoto M., Keika K., Motoba T., Anderson B., Nomura R., Fujimoto A., Shinohara I., Miyoshi Y.

    Journal of Geophysical Research: Space Physics   123 巻 ( 11 ) 頁: 9545 - 9559   2018年11月

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    記述言語:日本語   掲載種別:研究論文(学術雑誌)   出版者・発行元:Journal of Geophysical Research: Space Physics  

    Storm-time region-2 field-aligned currents (R2 FACs) are believed to be connected between the ring current region and the ionosphere, but this connection has not been clarified by simultaneous in situ observations. We confirmed the connection of upward R2 FACs during 16 July and 18 June 2017 storm events using coordinated magnetic observations by the Arase satellite in medium-Earth orbit and the Active Magnetosphere and Planetary Electrodynamics Response Experiment (AMPERE). The upward FACs were determined by drastic changes in the azimuthal magnetic field at Arase in the off-equatorial (3- to 4-RE radial distance and 1–2 RE above the magnetic equator) postmidnight inner magnetosphere. The magnetic latitude of the FAC observed by Arase projected onto the ionosphere was consistent with that of the ionospheric FAC observed by the AMPERE. Using the conservation of the ratio between the current density and the total magnetic field along the field line, we showed that the current between Arase and AMPERE was almost conserved, meaning that a large portion of the R2 FAC was generated in the low-latitude inner magnetosphere. We also calculated the plasma pressures of H+ and O+ ions and pressure-driven currents to examine their relationship for the first event. The O+ pressure contributed significantly to the inner part of the total azimuthal current. The peaks of combined pressure of H+ and O+, and pressure-driven currents were located inside and outside the FAC, respectively. A simple model calculation indicated that this spatial relationship is controlled by the day-night asymmetry of magnetic field.

    DOI: 10.1029/2018JA025865

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  91. A Sensor Package for Space Weather Global Monitoring Based on Micro Satellite Constellation 査読有り

    Nagatsuma, T, A. Kumamoto, M. Ozaki, K. Kitamura, Y. Saito, T. Takashima, M. Nose, J. Kurihara, H. Kojima, K. Ishisaka, A. Matsuoka, R. Nomura, T. Ishida, Y. Takahashi

    TRANSACTIONS OF THE JAPAN SOCIETY FOR AERONAUTICAL AND SPACE SCIENCES, AEROSPACE TECHNOLOGY JAPAN   16 巻   頁: 687 - 690   2018年11月

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    記述言語:英語   掲載種別:研究論文(学術雑誌)  

    DOI: 10.2322/tastj.16.687

  92. Longitudinal Structure of Oxygen Torus in the Inner Magnetosphere: Simultaneous Observations by Arase and Van Allen Probe A 査読有り

    M. Nos{\'{e, A. Matsuoka, A. Kumamoto, Y. Kasahara, J. Goldstein, M. Teramoto, F. Tsuchiya, S. Matsuda, M. Shoji, S. Imajo, S. Oimatsu, K. Yamamoto, Y. Obana, R. Nomura, A. Fujimoto, I. Shinohara, Y. Miyoshi, W. S. Kurth, C. A. Kletzing, C. W. Smith, R. J. MacDowall

    Geophysical Research Letters   45 巻 ( 19 ) 頁: 10,177 - 10,184   2018年10月

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    記述言語:日本語   掲載種別:研究論文(学術雑誌)   出版者・発行元:American Geophysical Union ({AGU})  

    Simultaneous observations of the magnetic field and plasma waves made by the Arase and Van Allen Probe A satellites at different magnetic local time (MLT) enable us to deduce the longitudinal structure of an oxygen torus for the first time. During 04:00–07:10 UT on 24 April 2017, Arase flew from L = 6.2 to 2.0 in the morning sector and detected an enhancement of the average plasma mass up to ~3.5 amu around L = 4.9–5.2 and MLT = 5.0 hr, implying that the plasma consists of approximately 15% O+ ions. Probe A moved outbound from L = 2.0 to 6.2 in the afternoon sector during 04:10–07:30 UT and observed no clear enhancements in the average plasma mass. For this event, the O+ density enhancement in the inner magnetosphere (i.e., oxygen torus) does not extend over all MLT but is skewed toward the dawn, being described more precisely as a crescent-shaped torus or a pinched torus.

    DOI: 10.1029/2018GL080122

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  93. Purple auroral rays and global Pc1 pulsations observed at the CIR-associated solar wind density enhancement on March 21, 2017 査読有り

    Shiokawa, K, M. Ozaki, A. Kadokura, Y. Endo, T. Sakanoi, S. Kurita, Y. Miyoshi, S.-I. Oyama, M. Connors, I. Schofield, J. Michael Ruohoniemi, M. Nose, T. Nagatsuma, K. Sakaguchi, D. G. Baishev, A. Pashinin, R. Rakhmatulin, B. Shevtsov, I. Poddelsky, M. Engebretson, Tero Raita, Y.-M. Tanaka, M. Shinohara, M. Teramoto, R. Nomura, A. Fujimoto, A. Matsuoka, N. Higashio, T. Takashima, I. Shinohara, Jay M. Albert

    Geophys. Res. Lett.   45 巻 ( 20 ) 頁: 10,819 - 10,828   2018年9月

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    記述言語:英語   掲載種別:研究論文(学術雑誌)   出版者・発行元:Geophysical Research Letters  

    This paper reports two unique auroral features: postmidnight purple auroral rays and global Pc1 geomagnetic pulsations, observed before the onset of the corotating interaction region (CIR) storm of 21 March 2017, at the beginning of the first campaign of the new Particles and Waves in the Inner magnetosphere using Ground-based network observation (PWING) longitudinal ground network with the Arase satellite. The purple auroral rays were observed from ~0315 to 0430 UT (~03–04 magnetic local time) in the northeastern sky at Husafell, Iceland (magnetic latitude: 64.9°N). We newly propose that the entry of high-density CIR plasma into the magnetotail created purple auroral rays in the sunlit ionosphere. Pc1 geomagnetic pulsations at frequencies of 0–0.5 Hz were observed after ~00 UT over a wide local time range, of 13 hr, from midnight to afternoon sectors at subauroral latitudes associated with CIR arrival. These results indicate preconditioning of the magnetosphere due to crossing of a CIR.

    DOI: 10.1029/2018GL079103

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  94. Impulsively Excited Nightside Ultralow Frequency Waves Simultaneously Observed on and off the Magnetic Equator 査読有り

    Takahashi Kazue, Denton Richard E, Motoba Tetsuo, Matsuoka Ayako, Kasaba Yasumasa, Kasahara Yoshiya, Teramoto Mariko, Shoji Masafumi, Takahashi Naoko, Miyoshi Yoshizumi, Nose Masahito, Kumamoto Atsushi, Tsuchiya Fuminori, Redmon Robert J, Rodriguez Juan V

    GEOPHYSICAL RESEARCH LETTERS   45 巻 ( 16 ) 頁: 7918 - 7926   2018年8月

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    記述言語:英語   掲載種別:研究論文(学術雑誌)   出版者・発行元:Geophysical Research Letters  

    The Arase spacecraft is capable of observing ultralow frequency waves in the inner magnetosphere at intermediate magnetic latitudes, a region sparsely covered by previous spacecraft missions. We report a series of impulsively excited fundamental toroidal mode standing Alfvén waves in the midnight sector observed by Arase outside the plasmasphere at magnetic latitudes 13–24°. The wave onsets are concurrent with Pi2 onsets detected by the Van Allen Probe B spacecraft at the magnetic equator in the duskside plasmasphere and by ground magnetometers at low latitudes. The duration of each toroidal wave packet is ∼20 min, which is much longer than that of the corresponding Pi2 wave packet. The toroidal waves cannot be the source of high-latitude Pi2 waves because they were not detected on the ground near the magnetic field footprint of Arase. Overall, the toroidal wave event lasted more than 2 hr and allowed us to use the wave frequency to estimate the plasma mass density at L = 6.1–8.3. The mass density (in amu/cm3) is higher than the electron density (cm−3) by a factor of ∼6, which implies that 17–33% of the ions were O+.

    DOI: 10.1029/2018GL078731

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  95. Magnetic Field Dipolarization and Its Associated Ion Flux Variations in the Dawnside Deep Inner Magnetosphere: Arase Observations 査読有り

    M. Nos{\'{e, A. Matsuoka, S. Kasahara, S. Yokota, M. Teramoto, K. Keika, K. Yamamoto, R. Nomura, A. Fujimoto, N. Higashio, H. Koshiishi, S. Imajo, S. Oimatsu, Y. -M. Tanaka, M. Shinohara, I. Shinohara, Y. Miyoshi

    Geophysical Research Letters   45 巻 ( 16 ) 頁: 7942 - 7950   2018年8月

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    記述言語:日本語   掲載種別:研究論文(学術雑誌)   出版者・発行元:American Geophysical Union ({AGU})  

    The Arase satellite observed clear dipolarization signatures at r~4.3–4.6 RE, GMLAT~16°–18°, and MLT~5.5–5.7 hr around 15:00 UT on 27 March 2017 when Dst~−70 nT. Strong magnetic field fluctuations were embedded and their characteristic frequency was close to the local gyrofrequency of O+ ions. After the dipolarization, O+ flux was enhanced at ≤15 keV, while H+ flux showed no clear variations. These observations provide evidence for the direct supply of O+ ions from the ionosphere. There were no clear signatures for the nonadiabatic local acceleration of O+ ions. We consider that a bump-on-tail structure in the energy spectrum around 30–50 keV due to a combination of charge exchange loss and drift motion of ions masks the nonadiabatic acceleration. Occurrence of the magnetic field dipolarization at dawn, which is far from the well-known premidnight occurrence peak, may be due to an eastward skewing of partial ring current during the storm main phase.

    DOI: 10.1029/2018GL078825

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  96. Drift-Bounce Resonance Between Pc5 Pulsations and Ions at Multiple Energies in the Nightside Magnetosphere: Arase and MMS Observations 査読有り

    S. Oimatsu, M. Nos{\'{e, M. Teramoto, K. Yamamoto, A. Matsuoka, S. Kasahara, S. Yokota, K. Keika, G. Le, R. Nomura, A. Fujimoto, D. Sormakov, O. Troshichev, Y.-M. Tanaka, M. Shinohara, I. Shinohara, Y. Miyoshi, J. A. Slavin, R. E. Ergun, P.-A. Lindqvist

    Geophysical Research Letters   45 巻 ( 15 ) 頁: 7277 - 7286   2018年8月

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    記述言語:日本語   掲載種別:研究論文(学術雑誌)   出版者・発行元:American Geophysical Union ({AGU})  

    A Pc5 wave is observed by the Exploration of energization and Radiation in Geospace Arase satellite in the inner magnetosphere (L ~5.4–6.1) near postmidnight (L-magnetic local time ~1.8–2.5 hr) during the storm recovery phase on 27 March 2017. Its azimuthal wave number (m-number) is estimated using two independent methods with satellites and ground observations to be −8 to −15. The direct measurement of the m-number enables us to calculate the resonance energy. The flux oscillations of H+ and O+ ions at ≥ 56.3 keV are caused by drift resonance and those of O+ ions at ≤ 18.6 keV by bounce resonance. Resonances of O+ ions at multiple energies are simultaneously observed for the first time. The enhancement of the O+/H+ flux ratio at ≤ 18.6 keV indicates selective acceleration of O+ ions through bounce resonance.

    DOI: 10.1029/2018GL078961

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  97. Giant Pulsations Excited by a Steep Earthward Gradient of Proton Phase Space Density: Arase Observation 査読有り

    Kazuhiro Yamamoto, Masahito Nos{\'{e, Satoshi Kasahara, Shoichiro Yokota, Kunihiro Keika, Ayako Matsuoka, Mariko Teramoto, Kazue Takahashi, Satoshi Oimatsu, Reiko Nomura, Massimo Vellante, Bal{\'{a } }zs Heilig, Akiko Fujimoto, Yoshimasa Tanaka, Manabu Shinohara, Iku Shinohara, Yoshizumi Miyoshi

    Geophysical Research Letters   45 巻 ( 14 ) 頁: 6773 - 6781   2018年7月

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    記述言語:英語   掲載種別:研究論文(学術雑誌)   出版者・発行元:American Geophysical Union ({AGU})  

    We present observational evidence of drift resonance between westward propagating odd mode standing ultralow frequency waves and energetic protons. Compressional ∼13 mHz (Pc4 band) waves and proton flux oscillations at >50 keV were detected at ∼03 hr magnetic local time by the Arase satellite on 15 April 2017. The azimuthal wave number (m number) is estimated to be ∼−50 from ground observations, while the theory of drift resonance gives m ∼− 49 for odd mode waves and ∼110-keV protons, providing evidence that the drift resonance indeed took place in this event. We also found a steep earthward gradient of proton phase space density, which can quantitatively explain the wave excitation. The observed waves show typical features of giant pulsations (Pgs), regarding local time, m number, and flux oscillations. This study, therefore, has great implications to the field line mode structure and excitation mechanism of Pgs.

    DOI: 10.1029/2018GL078293

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  98. Van Allen Probes Observations of Drift-Bounce Resonance and Energy Transfer Between Energetic Ring Current Protons and Poloidal Pc4 Wave 査読有り

    S. Oimatsu, M. Nosé, K. Takahashi, K. Yamamoto, K. Keika, C. A. Kletzing, C. W. Smith, R. J. MacDowall, D. G. Mitchell

    Journal of Geophysical Research: Space Physics   123 巻 ( 5 ) 頁: 3421 - 3435   2018年5月

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    記述言語:英語   掲載種別:研究論文(学術雑誌)   出版者・発行元:Blackwell Publishing Ltd  

    A poloidal Pc4 wave and proton flux oscillations are observed in the inner magnetosphere on the dayside near the magnetic equator by the Van Allen Probes spacecraft on 2 March 2014. The flux oscillations are observed in the energy range of 67.0 to 268.8 keV with the same frequency of the poloidal Pc4 wave. We find pitch angle and energy dispersion in the phase difference between the poloidal magnetic field and the proton flux oscillations, which are features of drift-bounce resonance. We estimate the resonance energy to be ~120 keV for pitch angle (α) of 30° or 150° and 170–180 keV for α = 50° or 130°. To examine the direction of energy flow between protons and the wave, we calculate the sign of the gradient of proton phase space density (df/dW) on both the inbound and outbound legs of the orbit. We find the gradient to be outward on both legs, which means that energy is transferred from the protons to the wave. During the poloidal Pc4 wave event, the Dst* index shows a measurable increase of ~6.7 nT. We estimate the total energy loss of the ring current from the recovery of the Dst* index and from the variation of proton flux by the drift-bounce resonance. We suggest that energy transfer from the ring current protons to the poloidal Pc4 wave via the drift-bounce resonance contributes to up to ~85% of the increase of the Dst* index.

    DOI: 10.1029/2017JA025087

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  99. Initial Results of EMIC Observation by MGF/Arase 査読有り

    Nomura R, Matsuoka A, Teramoto M, Miyoshi Y, Matsuda S, Kurita S, Keika K, Nose M, Shoji M, Fujimoto A, Shinohara M, Tanaka Y, Kasahara Y, Kasaba Y, Ishisaka K

    2018 2nd URSI Atlantic Radio Science Meeting, AT-RASC 2018     2018年5月

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    記述言語:日本語   掲載種別:研究論文(学術雑誌)   出版者・発行元:2018 2nd URSI Atlantic Radio Science Meeting, AT-RASC 2018  

    The Electromagnetic ion cyclotron (EMIC) wave is one of the key phenomena to understand the loss dynamics of MeV-energy electrons in the Earth's radiation belt. The precipitation into the ionosphere of MeV-energy electrons was observed in the isolated proton aurora which is an ionospheric footprint for the region of EMIC wave-particle interaction in the magnetosphere [1]. However, it is still unclear how significant the EMIC wave is in terms of the global scale of the whole radiation belt, and it is important to understand where and when the preferable condition is set in the radiation belt of the inner magnetosphere for strong EMIC waves.

    DOI: 10.23919/URSI-AT-RASC.2018.8471561

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    その他リンク: http://orcid.org/0000-0002-8160-3553

  100. Theory, modeling, and integrated studies in the Arase (ERG) project 査読有り

    Seki K., Miyoshi Y., Ebihara Y., Katoh Y., Amano T., Saito S., Shoji M., Nakamizo A., Keika K., Hori T., Nakano S.y., Watanabe S., Kamiya K., Takahashi N., Omura Y., Nose M., Fok M.C., Tanaka T., Ieda A., Yoshikawa A.

    Earth, Planets and Space   70 巻 ( 1 )   2018年2月

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    記述言語:英語   掲載種別:研究論文(学術雑誌)   出版者・発行元:Earth, Planets and Space  

    Understanding of underlying mechanisms of drastic variations of the near-Earth space (geospace) is one of the current focuses of the magnetospheric physics. The science target of the geospace research project Exploration of energization and Radiation in Geospace (ERG) is to understand the geospace variations with a focus on the relativistic electron acceleration and loss processes. In order to achieve the goal, the ERG project consists of the three parts: the Arase (ERG) satellite, ground-based observations, and theory/modeling/integrated studies. The role of theory/modeling/integrated studies part is to promote relevant theoretical and simulation studies as well as integrated data analysis to combine different kinds of observations and modeling. Here we provide technical reports on simulation and empirical models related to the ERG project together with their roles in the integrated studies of dynamic geospace variations. The simulation and empirical models covered include the radial diffusion model of the radiation belt electrons, GEMSIS-RB and RBW models, CIMI model with global MHD simulation REPPU, GEMSIS-RC model, plasmasphere thermosphere model, self-consistent wave–particle interaction simulations (electron hybrid code and ion hybrid code), the ionospheric electric potential (GEMSIS-POT) model, and SuperDARN electric field models with data assimilation. ERG (Arase) science center tools to support integrated studies with various kinds of data are also briefly introduced.[Figure not available: see fulltext.].

    DOI: 10.1186/s40623-018-0785-9

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  101. Three-Step Buildup of the 17 March 2015 Storm Ring Current: Implication for the Cause of the Unexpected Storm Intensification 査読有り

    Keika K., Seki K., Nosé M., Miyoshi Y., Lanzerotti L.J., Mitchell D.G., Gkioulidou M., Manweiler J.W.

    Journal of Geophysical Research: Space Physics   123 巻 ( 1 ) 頁: 414 - 428   2018年1月

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    記述言語:英語   掲載種別:研究論文(学術雑誌)   出版者・発行元:Journal of Geophysical Research: Space Physics  

    We examine the spatiotemporal variations of the energy density and the energy spectral evolution of energetic ions in the inner magnetosphere during the main phase of the 17 March 2015 storm, using data from the RBSPICE and EMFISIS instruments onboard Van Allen Probes. The storm developed in response to two southward IMF intervals separated by about 3 h. In contrast to two steps seen in the Dst/SYM-H index, the ring current ion population evolved in three steps: the first subphase was apparently caused by the earlier southward IMF, and the subsequent subphases occurred during the later southward IMF period. Ion energy ranges that contribute to the ring current differed between the three subphases. We suggest that the spectral evolution resulted from the penetration of different plasma sheet populations. The ring current buildup during the first subphase was caused by the penetration of a relatively low-energy population that had existed in the plasma sheet during a prolonged prestorm northward IMF interval. The deeper penetration of the lower-energy population was responsible for the second subphase. The third subphase, where the storm was unexpectedly intensified to a Dst/SYM-H level of <−200 nT, was caused by the penetration of a hot, dense plasma sheet population. We attribute the hot, dense population to the entry of hot, dense solar wind into the plasma sheet and/or ion heating/acceleration in the near-Earth plasma sheet associated with magnetotail activity such as reconnection and dipolarization.

    DOI: 10.1002/2017JA024462

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  102. Van Allen Probes Observations of Second Harmonic Poloidal Standing Alfvén Waves 査読有り

    Kazue Takahashi, Satoshi Oimatsu, Masahito Nos{\'{e, Kyungguk Min, Seth G. Claudepierre, Anthony Chan, John Wygant, Hyomin Kim

    Journal of Geophysical Research: Space Physics   123 巻 ( 1 ) 頁: 611 - 637   2018年1月

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    記述言語:英語   掲載種別:研究論文(学術雑誌)   出版者・発行元:American Geophysical Union ({AGU})  

    DOI: 10.1002/2017JA024869

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  103. Simultaneous observation of auroral substorm onset in Polar satellite global images and ground-based all-sky images. 査読有り

    Ieda A, Kauristie K, Nishimura Y, Miyashita Y, Frey HU, Juusola L, Whiter D, Nosé M, Fillingim MO, Honary F, Rogers NC, Miyoshi Y, Miura T, Kawashima T, Machida S

    Earth, planets, and space : EPS   70 巻 ( 1 ) 頁: 73   2018年

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    記述言語:英語   掲載種別:研究論文(学術雑誌)   出版者・発行元:Earth, Planets and Space  

    Substorm onset has originally been defined as a longitudinally extended sudden auroral brightening (Akasofu initial brightening: AIB) followed a few minutes later by an auroral poleward expansion in ground-based all-sky images (ASIs). In contrast, such clearly marked two-stage development has not been evident in satellite-based global images (GIs). Instead, substorm onsets have been identified as localized sudden brightenings that expand immediately poleward. To resolve these differences, optical substorm onset signatures in GIs and ASIs are compared in this study for a substorm that occurred on December 7, 1999. For this substorm, the Polar satellite ultraviolet global imager was operated with a fixed-filter (170 nm) mode, enabling a higher time resolution (37 s) than usual to resolve the possible two-stage development. These data were compared with 20-s resolution green-line (557.7 nm) ASIs at Muonio in Finland. The ASIs revealed the AIB at 2124:50 UT and the subsequent poleward expansion at 2127:50 UT, whereas the GIs revealed only an onset brightening that started at 2127:49 UT. Thus, the onset in the GIs was delayed relative to the AIB and in fact agreed with the poleward expansion in the ASIs. The fact that the AIB was not evident in the GIs may be attributed to the limited spatial resolution of GIs for thin auroral arc brightenings. The implications of these results for the definition of substorm onset are discussed herein.[Figure not available: see fulltext.].

    DOI: 10.1186/s40623-018-0843-3

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  104. Initial results of EMIC observation by MGF/Arase

    Nomura R., Matsuoka A., Teramoto M., Miyoshi Y., Matsuda S., Kurita S., Keika K., Nose M., Shoji M., Fujimoto A., Shinohara M., Tanaka Y., Kasahara Y., Kasaba Y., Ishisaka K.

    2018 2ND URSI ATLANTIC RADIO SCIENCE MEETING (AT-RASC)     頁: .   2018年

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    記述言語:英語   掲載種別:研究論文(学術雑誌)  

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  105. Ground-based instruments of the PWING project to investigate dynamics of the inner magnetosphere at subauroral latitudes as a part of the ERG-ground coordinated observation network 査読有り

    Shiokawa K., Katoh Y., Hamaguchi Y., Yamamoto Y., Adachi T., Ozaki M., Oyama S.I., Nosé M., Nagatsuma T., Tanaka Y., Otsuka Y., Miyoshi Y., Kataoka R., Takagi Y., Takeshita Y., Shinbori A., Kurita S., Hori T., Nishitani N., Shinohara I., Tsuchiya F., Obana Y., Suzuki S., Takahashi N., Seki K., Kadokura A., Hosokawa K., Ogawa Y., Connors M., Michael Ruohoniemi J., Engebretson M., Turunen E., Ulich T., Manninen J., Raita T., Kero A., O'Ksanen A., Back M., Kauristie K., Mattanen J., Baishev D., Kurkin V., Oinats A., Pashinin A., Vasilyev R., Rakhmatulin R., Bristow W., Karjala M.

    Earth, Planets and Space   69 巻 ( 1 )   2017年11月

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    記述言語:英語   掲載種別:研究論文(学術雑誌)   出版者・発行元:Earth, Planets and Space  

    The plasmas (electrons and ions) in the inner magnetosphere have wide energy ranges from electron volts to mega-electron volts (MeV). These plasmas rotate around the Earth longitudinally due to the gradient and curvature of the geomagnetic field and by the co-rotation motion with timescales from several tens of hours to less than 10 min. They interact with plasma waves at frequencies of mHz to kHz mainly in the equatorial plane of the magnetosphere, obtain energies up to MeV, and are lost into the ionosphere. In order to provide the global distribution and quantitative evaluation of the dynamical variation of these plasmas and waves in the inner magnetosphere, the PWING project (study of dynamical variation of particles and waves in the inner magnetosphere using ground-based network observations, http://www.isee.Nagoya-u.ac.jp/dimr/PWING/) has been carried out since April 2016. This paper describes the stations and instrumentation of the PWING project. We operate all-sky airglow/aurora imagers, 64-Hz sampling induction magnetometers, 40-kHz sampling loop antennas, and 64-Hz sampling riometers at eight stations at subauroral latitudes (~ 60° geomagnetic latitude) in the northern hemisphere, as well as 100-Hz sampling EMCCD cameras at three stations. These stations are distributed longitudinally in Canada, Iceland, Finland, Russia, and Alaska to obtain the longitudinal distribution of plasmas and waves in the inner magnetosphere. This PWING longitudinal network has been developed as a part of the ERG (Arase)-ground coordinated observation network. The ERG (Arase) satellite was launched on December 20, 2016, and has been in full operation since March 2017. We will combine these ground network observations with the ERG (Arase) satellite and global modeling studies. These comprehensive datasets will contribute to the investigation of dynamical variation of particles and waves in the inner magnetosphere, which is one of the most important research topics in recent space physics, and the outcome of our research will improve safe and secure use of geospace around the Earth.[Figure not available: see fulltext.]

    DOI: 10.1186/s40623-017-0745-9

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  106. Characteristics of Seasonal Variation and Solar Activity Dependence of the Geomagnetic Solar Quiet Daily Variation 査読有り

    Shinbori A., Koyama Y., Nosé M., Hori T., Otsuka Y.

    Journal of Geophysical Research: Space Physics   122 巻 ( 10 ) 頁: 10 - 810   2017年10月

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    記述言語:英語   掲載種別:研究論文(学術雑誌)   出版者・発行元:Journal of Geophysical Research: Space Physics  

    Characteristics of seasonal variation and solar activity dependence of the X and Y components of the geomagnetic solar quiet (Sq) daily variation at Memambetsu in midlatitudes and Guam near the equator have been investigated using long-term geomagnetic field data with 1 h time resolution from 1957 to 2016. The monthly mean Sq variation in the X and Y components (Sq-X and Sq-Y) shows a clear seasonal variation and solar activity dependence. The amplitude of seasonal variation increases significantly during high solar activities and is proportional to the solar F10.7 index. The pattern of the seasonal variation is quite different between Sq-X and Sq-Y. The result of the correlation analysis between the solar F10.7 index and the Sq-X and Sq-Y shows an almost linear relationship, but the slope of the linear fitted line varies as a function of local time and month. This implies that the sensitivity of Sq-X and Sq-Y to the solar activity is different for different local times and seasons. The pattern of the local time and seasonal variations of Sq-Y at Guam shows good agreement with that of a magnetic field produced by interhemispheric field-aligned currents (FACs), which flow from the summer to winter hemispheres in the dawn and dusk sectors and from the winter to summer hemispheres in the prenoon to afternoon sectors. The direction of the interhemispheric FAC in the dusk sector is opposite to the concept of Fukushima's model.

    DOI: 10.1002/2017JA024342

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  107. Ionospheric Alfvén resonator observed at low-latitude ground station, Muroto 査読有り

    M. Nos{\'{e, M. Uyeshima, J. Kawai, H. Hase

    Journal of Geophysical Research: Space Physics   122 巻 ( 7 ) 頁: 7240 - 7255   2017年7月

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    記述言語:英語   掲載種別:研究論文(学術雑誌)   出版者・発行元:American Geophysical Union ({AGU})  

    DOI: 10.1002/2017JA024204

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  108. Long-term variations in the plasma sheet ion composition and substorm occurrence over 23 years 査読有り

    Masahito Nose

    Geoscience Letters   3 巻 ( 1 )   2016年12月

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    記述言語:英語   掲載種別:研究論文(学術雑誌)   出版者・発行元:Springer Science $\mathplus$ Business Media  

    DOI: 10.1186/s40562-015-0033-0

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  109. Van Allen Probes observations of magnetic field dipolarization and its associated O<sup>+</sup> flux variations in the inner magnetosphere at L &lt; 6.6 査読有り

    Nosé M., Keika K., Kletzing C.A., Spence H.E., Smith C.W., MacDowall R.J., Reeves G.D., Larsen B.A., Mitchell D.G.

    Journal of Geophysical Research: Space Physics   121 巻 ( 8 ) 頁: 7572 - 7589   2016年8月

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    記述言語:英語   掲載種別:研究論文(学術雑誌)   出版者・発行元:Journal of Geophysical Research: Space Physics  

    We investigate the magnetic field dipolarization in the inner magnetosphere and its associated ion flux variations, using the magnetic field and energetic ion flux data acquired by the Van Allen Probes. From a study of 74 events that appeared at L = 4.5–6.6 between 1 October 2012 and 31 October 2013, we reveal the following characteristics of the dipolarization in the inner magnetosphere: (1) its time scale is approximately 5 min; (2) it is accompanied by strong magnetic fluctuations that have a dominant frequency close to the O+ gyrofrequency; (3) ion fluxes at 20–50 keV are simultaneously enhanced with larger magnitudes for O+ than for H+; (4) after a few minutes of the dipolarization, the flux enhancement at 0.1–5 keV appears with a clear energy-dispersion signature only for O+; and (5) the energy-dispersed O+ flux enhancement appears in directions parallel or antiparallel to the magnetic field. From these characteristics, we discuss possible mechanisms that can provide selective acceleration to O+ ions at >20 keV. We conclude that O+ ions at L = 5.4–6.6 undergo nonadiabatic local acceleration caused by oscillating electric field associated with the magnetic fluctuations and/or adiabatic convective transport from the plasma sheet to the inner magnetosphere by the impulsive electric field. At L = 4.5–5.4, however, only the former acceleration is plausible. We also conclude that the field-aligned energy-dispersed O+ ions at 0.1–5 keV originate from the ionosphere and are extracted nearly simultaneously to the onset of the dipolarization.

    DOI: 10.1002/2016JA022549

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  110. Storm time impulsive enhancements of energetic oxygen due to adiabatic acceleration of preexisting warm oxygen in the inner magnetosphere 査読有り

    Keika K., Seki K., Nosé M., Machida S., Miyoshi Y., Lanzerotti L.J., Mitchell D.G., Gkioulidou M., Turner D., Spence H., Larsen B.A.

    Journal of Geophysical Research: Space Physics   121 巻 ( 8 ) 頁: 7739 - 7752   2016年8月

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    記述言語:英語   掲載種別:研究論文(学術雑誌)   出版者・発行元:Journal of Geophysical Research: Space Physics  

    We examine enhancements of energetic (>50 keV) oxygen ions observed by the Radiation Belt Storm Probes Ion Composition Experiment (RBSPICE) instrument on board the Van Allen Probes spacecraft in the inner magnetosphere (L ~ 6) at 22–23 h magnetic local time (MLT) during an injection event of the 6 June 2013 storm. Simultaneous observations by two Van Allen Probes spacecraft located close together (~0.5 RE) indicate that particle injections occurred in the premidnight sector (< ~24 h MLT). We also examine the evolution of the proton and oxygen energy spectra at L ~ 6 during the injection event. The spectral slope did not significantly change during the storm. The oxygen phase space density (PSD) was shifted toward higher PSD in a wide range of the first adiabatic invariant. The spectral evolution manifests the characteristics of adiabatic acceleration and density increase of oxygen ions. Warm (0.1–10 keV) oxygen measured by the Helium, Oxygen, Proton, and Electron (HOPE) instrument was enhanced prior to the storm mostly in magnetic field-aligned directions. The most reasonable scenario of this event is that warm oxygen ions that preexisted in the inner magnetosphere were picked up and adiabatically transported and accelerated by spatially localized, temporarily impulsive electric fields.

    DOI: 10.1002/2016JA022384

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  111. Estimation of magnetospheric plasma ion composition for 1956-1975 by using high time resolution geomagnetic field data created from analog magnetograms 査読有り

    K. Yamamoto, M. Nose, N. Mashiko, K. Morinaga, S. Nagamachi

    JOURNAL OF GEOPHYSICAL RESEARCH-SPACE PHYSICS   121 巻 ( 6 ) 頁: 5203 - 5212   2016年6月

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    記述言語:英語   掲載種別:研究論文(学術雑誌)   出版者・発行元:AMER GEOPHYSICAL UNION  

    This study addresses the ion composition in the magnetosphere before the satellite era. We estimate the plasma ion mass for 1956-1975 from the period of low-latitude Pi2 pulsations found in digital geomagnetic field data that are created from analog magnetograms at Kakioka. The period of investigation covers most of solar cycle 19 and the whole solar cycle 20. To consider long-term variation, the moving average of the estimated plasma ion mass is calculated with a 1 year time window. We find that 1 year moving average of the plasma ion mass changed by a factor of similar to 2 during one solar cycle (i.e., between similar to 1.1 amu and similar to 2.4 amu for solar cycle 19 and between similar to 1.1 amu and similar to 2.0 amu for solar cycle 20). The correlation coefficient between the 1 year moving average of the plasma ion mass and that of the F-10.7 index is 0.86. This result supports the idea that in long-term variation, solar radiation increases the density and the temperature of O+ ions in the ionosphere, leads to the outflow of O+ ions, and contributes to the enhancement of the plasma ion mass in the nightside magnetosphere. The digital data created from analog magnetograms provide an important clue to know the space environment in old days and are advantageous for studies of the space weather and space climate.

    DOI: 10.1002/2016JA022510

    Web of Science

  112. JavaFX-based iUgonet Data Analysis Software (JudasFX)のプロトタイプ開発 査読有り

    小山幸伸, 佐藤由佳, 中野慎也, 八木学, 田中良昌, 阿部修司, 能勢正仁, 蔵川圭, 池田大輔, 梅村宜生, 新堀淳樹, 上野悟

    宇宙科学情報解析論文誌   ( 5 ) 頁: 81 - 92   2016年3月

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    記述言語:日本語   掲載種別:研究論文(学術雑誌)  

  113. Subpacket structures in EMIC rising tone emissions observed by the THEMIS probes 査読有り

    Satoko Nakamura, Yoshiharu Omura, Masafumi Shoji, Masahito Nosé, Danny Summers, Vassilis Angelopoulos

    Journal of Geophysical Research: Space Physics   120 巻 ( 9 ) 頁: 7318 - 7330   2015年9月

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    記述言語:英語   掲載種別:研究論文(学術雑誌)   出版者・発行元:American Geophysical Union (AGU)  

    DOI: 10.1002/2014JA020764

    Web of Science

    CiNii Research

  114. Multipoint observation of the response of the magnetosphere and ionosphere related to the sudden impulse event on 19 November 2007 査読有り

    Antoni Segarra, Masahito Nose, Juan Jose Curto, Tohru Araki

    JOURNAL OF SPACE WEATHER AND SPACE CLIMATE   5 巻   2015年6月

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    記述言語:英語   掲載種別:研究論文(学術雑誌)   出版者・発行元:EDP SCIENCES S A  

    The aim of this study is to provide a complete scope of a magnetic sudden impulse (SI) event along its way through interplanetary space and the magnetosphere until its arrival to the ground. In our case, we chose the event of 19th November 2007 because of the availability of enough well-located spacecraft at that moment for our purpose. We have used a 16 spacecraft data set. We calculated the mass flux variation and the change in magnetic field components across the discontinuity. Thus, we identified the solar wind discontinuity as a shock. We also calculated the orientation of the solar wind shock front. Then, we examined the effects of the shock front propagation in detail. With this large data set, we obtained a global view of the travelling wave front and identified the effects of the compressional wave front. Thus, we determined in detail the shock front passing through the different parts of the magnetosphere. We described the compressional effects in the bow shock, the magnetosheath, and the magnetopause and we depicted the propagation inside the inner magnetosphere. Moreover, we used an extensive data set from magnetic observatories on the ground and so we studied the global distribution of the SI waveform. Finally, the comparison of the observational facts with those derived from the theoretical model showed a good consistency. On the basis of the waveforms and polarizations of this SI, we determined the location in latitude where ionospheric currents (ICs) changed their sense. And also, we related polarization at ground to polarization measured by GOES spacecraft.

    DOI: 10.1051/swsc/2015016

    Web of Science

  115. Spatial structure and temporal evolution of energetic particle injections in the inner magnetosphere during the 14 July 2013 substorm event 査読有り

    Gkioulidou Matina, Ohtani S., Mitchell D. G., Ukhorskiy A. Y., Reeves G. D., Turner D. L., Gjerloev J. W., Nose M., Koga K., Rodriguez J. V., Lanzerotti L. J.

    JOURNAL OF GEOPHYSICAL RESEARCH-SPACE PHYSICS   120 巻 ( 3 ) 頁: 1924 - 1938   2015年3月

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    記述言語:日本語   掲載種別:研究論文(学術雑誌)  

    DOI: 10.1002/2014JA020872

    Web of Science

  116. CDF data archive and integrated data analysis platform for ERG-related ground data developed by ERG Science Center (ERG-SC) 査読有り

    Hori, T, Y. Miyashita, Y. Miyoshi, K. Seki, T. Segawa, Y.-M. Tanaka, K. Keika, M. Shoji, I. Shinohara, K. Shiokawa, Y. Otsuka, S. Abe, A. Yoshikawa, K. Yumoto, Y. Obana, N. Nishitani, A. S. Yukimatu, T. Nagatsuma, M. Kunitake, K. Hosokawa, Y. Ogawa, K. T. Murata, M. Nose, H. Kawano, T. Sakanoi

    宇宙航空研究開発機構研究開発報告: 宇宙科学情報解析論文誌   4 (JAXA-RR-14-009) 巻   頁: 75 - 89   2015年3月

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    記述言語:英語   掲載種別:研究論文(学術雑誌)  

    The Exploration of energization and Radiation in Geospace project Science Center (ERG-SC) has developed the science data file archive and integrated data analysis tool for the ground network observation data of the ERG project. We have organized data design consortiums to develop and elaborate the standard metadata and data variable sets for each type of the ERG-related ground data being archived as Common Data Format (CDF) files. The integrated data analysis software for the project has also been developed on the basis of the Space Physics Environment Data Analysis Software (SPEDAS) which works in concert with the CDF data file repository. The software tools, which are provided as plug-in libraries for SPEDAS, are made available to the international science community so that scientists and students are ready to proceed to integrated studies combining the ground data with other satellite and simulation data seamlessly. The integrated data analysis software can make scientific activities more productive and help the ERG project achieve the scientific goals.

  117. Formation of the oxygen torus in the inner magnetosphere: Van Allen Probes observations 査読有り

    Nose M., Oimatsu S., Keika K., Kletzing C. A., Kurth W. S., De Pascuale S., Smith C. W., MacDowall R. J., Nakano S., Reeves G. D., Spence H. E., Larsen B. A.

    JOURNAL OF GEOPHYSICAL RESEARCH-SPACE PHYSICS   120 巻 ( 2 ) 頁: 1182 - 1196   2015年2月

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    記述言語:日本語   掲載種別:研究論文(学術雑誌)   出版者・発行元:Journal of Geophysical Research: Space Physics  

    We study the formation process of an oxygen torus during the 12-15 November 2012 magnetic storm, using the magnetic field and plasma wave data obtained by Van Allen Probes. We estimate the local plasma mass density (ρL) and the local electron number density (neL) from the resonant frequencies of standing Alfvén waves and the upper hybrid resonance band. The average ion mass (M) can be calculated by M ∼ ρL/neL under the assumption of quasi-neutrality of plasma. During the storm recovery phase, both Probe A and Probe B observe the oxygen torus at L = 3.0-4.0 and L = 3.7-4.5, respectively, on the morning side. The oxygen torus has M = 4.5-8 amu and extends around the plasmapause that is identified at L∼3.2-3.9. We find that during the initial phase, M is 4-7 amu throughout the plasma trough and remains at ∼1 amu in the plasmasphere, implying that ionospheric O+ ions are supplied into the inner magnetosphere already in the initial phase of the magnetic storm. Numerical calculation under a decrease of the convection electric field reveals that some of thermal O+ ions distributed throughout the plasma trough are trapped within the expanded plasmasphere, whereas some of them drift around the plasmapause on the dawnside. This creates the oxygen torus spreading near the plasmapause, which is consistent with the Van Allen Probes observations. We conclude that the oxygen torus identified in this study favors the formation scenario of supplying O+ in the inner magnetosphere during the initial phase and subsequent drift during the recovery phase.

    DOI: 10.1002/2014JA020593

    Web of Science

    Scopus

  118. Responses of different ion species to fast plasma flows and local dipolarization in the plasma sheet 査読有り

    Ohtani S., Nosé M., Miyashita Y., Lui A.T.Y.

    Journal of Geophysical Research: Space Physics   120 巻 ( 1 ) 頁: 187 - 200   2015年1月

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    記述言語:英語   掲載種別:研究論文(学術雑誌)   出版者・発行元:Journal of Geophysical Research: Space Physics  

    We investigate the responses of different ion species (H+, He+, He++, and O+) to fast plasma flows and local dipolarization in the plasma sheet in terms of energy density. We use energetic (9-210 keV) ion composition measurements made by the Geotail satellite at r = 10∼31 RE. The results are summarized as follows: (1) whereas the O+-to-H+ ratio decreases with earthward flow velocity, it increases with tailward flow velocity with steeper Vx dependence for perpendicular flows than for parallel flows; (2) for fast earthward flows, the energy density of each ion species increases without any clear preference for heavy ions; (3) for fast tailward flows, the ion energy density initially increases, then it decreases to below the preceding levels except for O+; (4) the O+-to-H+ ratio does not increase through local dipolarization irrespective of dipolarization amplitude, background Bz, X distance, and Vx; (5) in general, the H+ and He++ ions behave similarly. Result (1) can be attributed to radial transport in the presence of the earthward gradient of the background O+-to-H+ ratio. Results (2) and (4) suggest that ion energization at local dipolarization is not mass dependent in the energy range of our interest because the ions are not magnetized irrespective of species. Result (3) can be attributed to the thinning of the plasma sheet and the preferable field-aligned escape of the H+ ions on the tailward side of the reconnection site. Result (5) suggests that the solar wind is the primary source of the high-energy H+ ions.

    DOI: 10.1002/2014JA020517

    Web of Science

    Scopus

  119. An Interactive Data Language software package to calculate ionospheric conductivity by using numerical models 査読有り

    Koyama Y., Shinbori A., Tanaka Y., Hori T., Nosé M., Oimatsu S.

    Computer Physics Communications   185 巻 ( 12 ) 頁: 3398 - 3405   2014年12月

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    記述言語:英語   掲載種別:研究論文(学術雑誌)   出版者・発行元:Computer Physics Communications  

    The Inter-university Upper atmosphere Global Observation NETwork (IUGONET) project focuses on handling ground-based observational data of the upper atmosphere. To this end, the project members have been developing a data analysis software package which is based on Interactive Data Language (IDL). Filling the spatial gaps in observational data requires the use of numerical models. In this paper,wediscuss an IDL software package for global ionospheric conductivity by integration of 3rd party numerical models. The model can be used to create further derived models.

    DOI: 10.1016/j.cpc.2014.08.011

    Web of Science

    Scopus

  120. Long-term variation in the upper atmosphere as seen in the geomagnetic solar quiet daily variation Geomagnetism 査読有り

    Shinbori A., Koyama Y., Nose M., Hori T., Otsuka Y., Yatagai A.

    Earth, Planets and Space   66 巻 ( 1 ) 頁: 1 - 20   2014年12月

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    記述言語:英語   掲載種別:研究論文(学術雑誌)   出版者・発行元:Earth, Planets and Space  

    Characteristics of long-term variation in the amplitude of solar quiet (Sq) geomagnetic field daily variation have been investigated using 1-h geomagnetic field data obtained from 69 geomagnetic observation stations within the period of 1947 to 2013. The Sq amplitude observed at these geomagnetic stations showed a clear dependence on the 10- to 12-year solar activity cycle and tended to be enhanced during each solar maximum phase. The Sq amplitude was the smallest around the minimum of solar cycle 23/24 in 2008 to 2009. The relationship between the solar F10.7 index and Sq amplitude was approximately linear but about 53% of geomagnetic stations showed a weak nonlinear relation to the solar F10.7 index. In order to remove the effect of solar activity seen in the long-term variation of the Sq amplitude, we calculated a linear or second-order fitting curve between the solar F10.7 index and Sq amplitude during 1947 to 2013 and examined the residual Sq amplitude, which is defined as the deviation from the fitting curve. As a result, the majority of trends in the residual Sq amplitude that passed through a trend test showed negative values over a wide region. This tendency was relatively strong in Europe, India, the eastern part of Canada, and New Zealand. The relationship between the magnetic field intensity at 100-km altitude and residual Sq amplitude showed an anti-correlation for about 71% of the geomagnetic stations. Furthermore, the residual Sq amplitude at the equatorial station (Addis Ababa) was anti-correlated with the absolute value of the magnetic field inclination. This implies movement of the equatorial electrojet due to the secular variation of the ambient magnetic field.

    DOI: 10.1186/s40623-014-0155-1

    Web of Science

    Scopus

  121. 世界科学データシステム(WDS)のための学際的科学データ表示Webの提案

    村田 健史, 鵜川 健太郎, 村永 和哉, 鈴木 豊, 渡邉 英伸, 是津 耕司, 山本 和憲, 篠原 育, 笠原 禎也, 岡田 雅樹, 小嶋 浩嗣, 能勢 正仁, 木村 映善, 建部 修見, 田中 昌宏

    情報知識学会誌   24 巻 ( 3 ) 頁: 297 - 320   2014年10月

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    記述言語:日本語   掲載種別:研究論文(学術雑誌)   出版者・発行元:情報知識学会  

    世界科学会議(ICSU)のプログラムの一つである世界科学データシステム(WDS)は科学データに関する国際的取組を目的としており,異分野横断型研究対応を主要目標の一つとして掲げている.NICTサイエンスクラウドは,WDSの理念を実現するために次世代型の科学研究環境の実現を目的に構築された科学研究用クラウドシステムである.科学分野のビッグデータの収集・転送機能,保存・公開機能,処理・可視化機能をマッシュアップすることで学際的研究環境の実現が期待される.本研究では,科学データを融合して表示するための学際的科学データ表示Webを提案する.過去の 経験をもとに,まず学際的科学データ表示Webで必要な要件をまとめた.さらに基本設計を行い, 2 つの科学衛星プロジェクトデータを融合表示するWebアプリケーションをNICTサイエンスクラウド上に実装した.この実装事例をもとに,学際的科学データ表示Webの有効性について議論する.

    DOI: 10.2964/jsik_2014_030

    CiNii Research

  122. Statistical visualization of the Earth's magnetotail and the implied mechanism of substorm triggering based on superposed-epoch analysis of THEMIS data 査読有り

    Machida S., Miyashita Y., Ieda A., Nose M., Angelopoulos V., McFadden J. P.

    ANNALES GEOPHYSICAE   32 巻 ( 2 ) 頁: 99 - 111   2014年

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    記述言語:日本語   掲載種別:研究論文(学術雑誌)   出版者・発行元:Annales Geophysicae  

    To investigate the physical mechanism responsible for substorm triggering, we performed a superposed-epoch analysis using plasma and magnetic-field data from THEMIS probes. Substorm onset timing was determined based on auroral breakups detected by all-sky imagers at the THEMIS ground-based observatories. We found earthward flows associated with north-south auroral streamers during the substorm growth phase. At around <i>X</i> Combining double low line &minus;12 Earth radii (<i>R</i>E), the northward magnetic field and its elevation angle decreased markedly approximately 4 min before substorm onset. Moreover, a northward magnetic-field increase associated with pre-onset earthward flows was found at around <i>X</i> Combining double low line &minus;17 <i>R</i>E. This variation indicates that local dipolarization occurs. Interestingly, in the region earthwards of <i>X</i> Combining double low line &minus;18 <i>R</i>E, earthward flows in the central plasma sheet (CPS) reduced significantly approximately 3 min before substorm onset, which was followed by a weakening of dawn-/duskward plasma-sheet boundary-layer flows (subject to a 1 min time lag). Subsequently, approximately 1 min before substorm onset, earthward flows in the CPS were enhanced again and at the onset, tailward flows started at around <i>X</i> Combining double low line &minus;20 <i>R</i>E. Following substorm onset, an increase in the northward magnetic field caused by dipolarization was found in the near-Earth region. Synthesizing these results, we confirm our previous results based on GEOTAIL data, which implied that significant variations start earlier than both current disruption and magnetic reconnection, at approximately 4 min before substorm onset roughly halfway between the two regions of interest; i.e. in the catapult current sheet.©Author(s) 2014. CC Attribution 3.0 License.

    DOI: 10.5194/angeo-32-99-2014

    Web of Science

    Scopus

  123. Interuniversity upper atmosphere global observation network (IUGONET) metadata database and analysis software 査読有り

    Yatagai, A, Y.-M. Tanaka, S. Abe, A. Shinbori, M. Yagi, S. UeNo, Y. Koyama, N. Umemura, M. Nose, T. Hori, Y. Sato, N. O. Hashiguchi, N. Kaneda, IUGONET project team

    Data Science Journal   13 巻 ( 13 ) 頁: PDA37 - PDA43   2014年

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    記述言語:英語   掲載種別:研究論文(学術雑誌)   出版者・発行元:Data Science Journal  

    An overview of the Interuniversity Upper atmosphere Global Observation NETwork (IUGONET) project is presented. This Japanese program is building a meta-database for ground-based observations of the upper atmosphere, in which metadata connected with various atmospheric radars and photometers, including those located in both polar regions, are archived. By querying the metadata database, researchers are able to access data file/information held by data facilities. Moreover, by utilizing our analysis software, users can download, visualize, and analyze upper-atmospheric data archived in or linked with the system. As a future development, we are looking to make our database interoperable with others.

    DOI: 10.2481/dsj.IFPDA-07

    Scopus

    CiNii Research

  124. Dynamics of Ions of Ionospheric Origin During Magnetic Storms: Their Acceleration Mechanism and Transport Path to Ring Current 査読有り

    M. Nosé, K. Takahashi, S. Ohtani, S. P. Christon, R. W. McEntire

    The Inner Magnetosphere: Physics and Modeling     頁: 61 - 71   2013年3月

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    記述言語:英語   掲載種別:論文集(書籍)内論文   出版者・発行元:American Geophysical Union  

    We investigated the spatial and temporal properties of the 9-210 keV/e ion composition in the near-Earth plasma sheet (at geocentric distance, r, of 8-15 RE), using energetic ion flux data acquired by the suprathermal ion composition spectrometer (STICS) sensor of the energetic particle and ion composition (EPIC) instrument onboard the Geotail spacecraft. We analyzed data covering 8.3 years to find the MLT-r distribution of the H+, He+, and O+ energy densities (as well as the He+/H+ and O+/H+ energy density ratios) as a function of the SYM-H index. We obtained the following results: (1) The energy density increases as SYM-H decreases
    (2) The energy density change depends on ion mass: the largest change occurs in O+ and the smallest change occurs in H+
    (3) The energy density shows a dawn-dusk asymmetry when SYM-H &lt
    - 50 nT, being larger on the duskside than on the dawnside
    and (4) The He+/H+ and O+/H+ energy density ratios in the plasma sheet are similar to those in the ring current. From these results we conclude that ionospheric He+ and O+ ions are transported to the plasma sheet, accelerated there by the dawn-to-dusk electric field in a mass-dependent manner (heavier ions gain more energy than lighter ions), and injected into the ring current region. Both the ion flux from the ionosphere and the energy gain in the plasma sheet become large when the geomagnetic disturbance becomes intense.

    DOI: 10.1029/155GM08

    Scopus

  125. Assessment of the auroral electrojet index performance under various geomagnetic conditions 査読有り

    Liou K., Takahashi K., Anderson B. J., Nose M., Iyemori T.

    JOURNAL OF ATMOSPHERIC AND SOLAR-TERRESTRIAL PHYSICS   92 巻   頁: 31 - 36   2013年1月

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    記述言語:日本語   掲載種別:研究論文(学術雑誌)  

    DOI: 10.1016/j.jastp.2012.09.017

    Web of Science

    J-GLOBAL

  126. Barometric and magnetic observations of vertical acoustic resonance and resultant generation of field-aligned current associated with earthquakes 査読有り

    Iyemori Toshihiko, Tanaka Yoshikazu, Odagi Yoko, Sano Yasuharu, Takeda Masahiko, Nose Masahito, Utsugi Mitsuru, Rosales Domingo, Choque Edwin, Ishitsuka Jose, Yamanaka Sadato, Nakanishi Kunihito, Matsumura Mitsuru, Shinagawa Hiroyuki

    EARTH PLANETS AND SPACE   65 巻 ( 8 ) 頁: 901 - 909   2013年

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    記述言語:日本語   掲載種別:研究論文(学術雑誌)  

    DOI: 10.5047/eps.2013.02.002

    Web of Science

    J-GLOBAL

  127. Wp index: A new substorm index derived from high-resolution geomagnetic field data at low latitude 査読有り

    M. Nose, T. Iyemori, L. Wang, A. Hitchman, J. Matzka, M. Feller, S. Egdorf, S. Gilder, N. Kumasaka, K. Koga, H. Matsumoto, H. Koshiishi, G. Cifuentes-Nava, J. J. Curto, A. Segarra, C. Celik

    SPACE WEATHER-THE INTERNATIONAL JOURNAL OF RESEARCH AND APPLICATIONS   10 巻 ( 8 )   2012年8月

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    記述言語:英語   掲載種別:研究論文(学術雑誌)   出版者・発行元:AMER GEOPHYSICAL UNION  

    Geomagnetic field data with high time resolution (typically 1 s) have recently become more commonly acquired by ground stations. Such high time resolution data enable identifying Pi2 pulsations which have periods of 40-150 s and irregular (damped) waveforms. It is well-known that pulsations of this type are clearly observed at mid-and low-latitude ground stations on the nightside at substorm onset. Therefore, with 1-s data from multiple stations distributed in longitude around the Earth's circumference, substorm onset can be regularly monitored. In the present study we propose a new substorm index, the Wp index (Wave and planetary), which reflects Pi2 wave power at low-latitude, using geomagnetic field data from 11 ground stations. We compare the Wp index with the AE and ASY indices as well as the electron flux and magnetic field data at geosynchronous altitudes for 11 March 2010. We find that significant enhancements of the Wp index mostly coincide with those of the other data. Thus the Wp index can be considered a good indicator of substorm onset. The Wp index, other geomagnetic indices, and geosynchronous satellite data are plotted in a stack for quick and easy search of substorm onset. The stack plots and digital data of the Wp index are available at the Web site (http://s-cubed.info) for public use. These products would be useful to investigate and understand space weather events, because substorms cause injection of intense fluxes of energetic electrons into the inner magnetosphere and potentially have deleterious impacts on satellites by inducing surface charging. Citation: Nose, M., et al. (2012), Wp index: A new substorm index derived from high-resolution geomagnetic field data at low latitude, Space Weather, 10, S08002, doi:10.1029/2012SW000785.

    DOI: 10.1029/2012SW000785

    Web of Science

  128. Revisiting the role of magnetic field fluctuations in nonadiabatic acceleration of ions during dipolarization 査読有り

    M. Nose, Y. Ono, S. P. Christon, A. T. Y. Lui

    JOURNAL OF GEOPHYSICAL RESEARCH-SPACE PHYSICS   117 巻 ( 2 )   2012年2月

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    記述言語:英語   掲載種別:研究論文(学術雑誌)   出版者・発行元:AMER GEOPHYSICAL UNION  

    Using energetic (9-212 keV/e) ion flux data obtained by the Geotail spacecraft, Ono et al. (2009) statistically examined changes in the energy density of H+ and O+ ions in the near-Earth plasma sheet during substorm-associated dipolarization. They found that ions are nonadiabatically accelerated by the electric field induced by the magnetic field fluctuations whose frequencies are close to their gyrofrequencies. The present paper revisits this result and finds it still holds.

    DOI: 10.1029/2012JA017518

    Web of Science

  129. The Energization and Radiation in Geospace (ERG) Project 査読有り

    Miyoshi, Y, T. Ono, T. Takashima, K. Asamura, M. Hirahara, Y. Kasaba, A. Matsuoka, H. Kojima, K. Shiokawa, K. Seki, M. Fujimoto, T. Nagatsuma, C.Z. Cheng, Y. Kazama, S. Kasahara, T. Mitani, H. Matsumoto, N. Higashio, A. Kumamoto, S. Yagitani, Y. Kasahara, K. Ishisaka, L. Blomberg, A. Fujimoto, Y. Katoh, Y. Ebihara, Y. Omura, M. Nose, T. Hori, Y. Miyashita, Y. Tanaka, T. Segawa, ERG working group

    Geophys. Monogr. Ser.   199 巻   頁: 103 - 116   2012年

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    記述言語:英語   掲載種別:研究論文(学術雑誌)   出版者・発行元:Geophysical Monograph Series  

    The Energization and Radiation in Geospace (ERG) project for solar cycle 24 will explore how relativistic electrons in the radiation belts are generated during space storms. This geospace exploration project consists of three research teams: the ERG satellite observation team, the ground-based network observation team, and the integrated data analysis/simulation team. Satellite observation will provide in situ measurements of features such as the plasma distribution function, electric and magnetic fields, and plasma waves, whereas remote sensing by ground-based observations using, for example, HF radars, magnetometers, optical instruments, and radio wave receivers will provide the global state of the geospace. Various kinds of data will be integrated and compared with numerical simulations for quantitative understanding. Such a synergetic approach is essential for comprehensive understanding of relativistic electron generation/loss processes through crossenergy and cross-regional coupling in which different plasma populations and regions are dynamically coupled with each other. In addition, the ERG satellite will utilize a new and innovative measurement technique for wave-particle interactions that can directly measure the energy exchange process between particles and plasma waves. In this paper, we briefly review some of the profound problems regarding relativistic electron accelerations and losses that will be solved by the ERG project, and we provide an overview of the project. © 2012. American Geophysical Union. All Rights Reserved.

    DOI: 10.1029/2012GM001304

    Web of Science

    Scopus

    その他リンク: http://orcid.org/0000-0002-8160-3553

  130. Pressure changes associated with substorm depolarization in the near-Earth plasma sheet (vol 116, A01299, 2011) 査読有り

    Y. Miyashita, S. Machida, A. Ieda, D. Nagata, Y. Kamide, M. Nose, K. Liou, T. Mukai, S. P. Christon, C. T. Russell, I. Shinohara, Y. Saito

    JOURNAL OF GEOPHYSICAL RESEARCH-SPACE PHYSICS   116 巻   2011年1月

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    記述言語:英語   掲載種別:研究論文(学術雑誌)   出版者・発行元:AMER GEOPHYSICAL UNION  

    DOI: 10.1029/2010JA016389

    Web of Science

  131. Erratum: Pressure changes associated with substorm depolarization in the near-Earth plasma sheet (Journal of Geophysical Research A: Space Physics 115 (A12239) DOI: 10.1029/2010JA015608) 査読有り

    Y. Miyashita, S. MacHida, A. Ieda, D. Nagata, Y. Kamide, M. Nosé, K. Liou, T. Mukai, S.P. Christon, C.T. Russell, I. Shinohara, Y. Saito

    Journal of Geophysical Research A: Space Physics   116 巻 ( 1 )   2011年

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    記述言語:英語   掲載種別:研究論文(学術雑誌)  

    DOI: 10.1029/2010JA016389

  132. Geomagnetic Indices 査読有り

    Menvielle Michel, Iyemori Toshihiko, Marchaudon Aurelie, Nose Masahito

    GEOMAGNETIC OBSERVATIONS AND MODELS   5 巻   頁: 183 - 228   2011年

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    記述言語:日本語   掲載種別:研究論文(学術雑誌)  

    Michel Menvielle, Toshihiko Iyemori, Aurélie Marchaudon, Masahito Nosé, 2011, &#039;Geomagnetic Indices&#039;, &lt;i&gt;Geomagnetic Observations and Models&lt;/i&gt;, pp. 183-228

    DOI: 10.1007/978-90-481-9858-0_8

    Web of Science

    その他リンク: http://orcid.org/0000-0002-2789-3588

  133. Magnetic Observatory Data and Metadata: Types and Availability 査読有り

    Reay Sarah J., Herzog Donald C., Alex Sobhana, Kharin Evgeny P., McLean Susan, Nose Masahito, Sergeyeva Natalia A.

    GEOMAGNETIC OBSERVATIONS AND MODELS   5 巻   頁: 149 - 181   2011年

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    記述言語:日本語   掲載種別:研究論文(学術雑誌)  

    Sarah J. Reay, Donald C. Herzog, Sobhana Alex, Evgeny P. Kharin, Susan McLean, Masahito Nosé, Natalia A. Sergeyeva, 2011, &#039;Magnetic Observatory Data and Metadata: Types and Availability&#039;, &lt;i&gt;Geomagnetic Observations and Models&lt;/i&gt;, pp. 149-181

    DOI: 10.1007/978-90-481-9858-0_7

    Web of Science

    その他リンク: http://orcid.org/0000-0002-2789-3588

  134. Magnetic local time dependence of geomagnetic disturbances contributing to the AU and AL indices 査読有り

    Tomita S., Nose M., Iyemori T., Toh H., Takeda M., Matzka J., Bjornsson G., Saemundsson T., Janzhura A., Troshichev O., Schwarz G.

    ANNALES GEOPHYSICAE   29 巻 ( 4 ) 頁: 673 - 678   2011年

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    記述言語:日本語   掲載種別:研究論文(学術雑誌)  

    DOI: 10.5194/angeo-29-673-2011

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    J-GLOBAL

  135. Geomagnetism and the Orientation of Temples in Thailand 査読有り

    Iyemori T, M. Hashizume, A. Saito, M. Nose, N. Choosakul, T. Tsuda, Y. Odagi

    Journal of the Siam Society, Vol.99     2011年

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    記述言語:英語   掲載種別:研究論文(学術雑誌)  

  136. Mass-dependent evolution of energetic neutral atoms energy spectra during storm time substorms: Implication for O+ nonadiabatic acceleration 査読有り

    K. Keika, P. C. Brandt, S. Ohtani, D. G. Mitchell, K. Min, M. Nose, T. Obara, H. Koshiishi, H. Matsumoto

    JOURNAL OF GEOPHYSICAL RESEARCH-SPACE PHYSICS   115 巻 ( 12 )   2010年12月

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    記述言語:英語   掲載種別:研究論文(学術雑誌)   出版者・発行元:AMER GEOPHYSICAL UNION  

    We examine the temporal variations of energy spectra of energetic neutral atoms (ENAs) detected by the High Energy Neutral Atom imager (HENA) onboard the Imager for Magnetopause-to-Aurora Global Exploration (IMAGE) satellite during three substorms on 21 October 2001 and three substorms on 19 March 2002; the substorms occurred during the storm main phase. The ENA energy used in the present study ranges from 10 to 198 keV for hydrogen and from 29 to 222 keV for oxygen. We use ENA data obtained from two independent areas of a HENA image, for which HENA lines of sight pass through the inner magnetosphere (similar to-6 RE &lt; X &lt; similar to-3 R-E around the magnetic equator) and the outer magnetosphere (X &lt; similar to-6 R-E around the magnetic equator). The analyses of the selected ENA data yield the following results: (1) The oxygen ENA flux displays 20-30 min bursts during all substorms, while the hydrogen ENA flux did not increase or less significantly increased than the oxygen flux. (2) The temporal evolution of energy spectra is mass dependent for all examined substorms. (3) For two of the substorms, the oxygen flux ratio between before and after a substorm increases with increasing energy, indicating the hardening of an O+ energy spectrum. (4) The flux ratio for the inner image area is comparable to or higher than that in the outer area. The results confirm that nonadiabatic acceleration with regard to the first adiabatic invariant did occur in the near-Earth magnetotail (X &gt; -8 R-E). Although the influence of the nonadiabatic acceleration appears in the inner magnetosphere (similar to-6 R-E &lt; X &lt; similar to-3 R-E) as well as the outer magnetosphere (similar to-8 R-E &lt; X &lt; similar to-6 R-E), it is not clear from the present results whether O+ energization in the inner magnetosphere is due to nonadiabatic acceleration in the inner magnetosphere or adiabatic transport of O+ nonadiabatically accelerated in the outer magnetosphere. It is likely, for at least the two substorms, that the nonadiabatic acceleration makes a more significant contribution to O+ energization than increase of the O+ density in the plasma sheet.

    DOI: 10.1029/2010JA015889

    Web of Science

  137. Excitation mechanism of low-latitude Pi2 pulsations: Cavity mode resonance or BBF-driven process? 査読有り

    Nose M.

    JOURNAL OF GEOPHYSICAL RESEARCH-SPACE PHYSICS   115 巻 ( 7 )   2010年7月

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    記述言語:英語   掲載種別:研究論文(学術雑誌)  

    DOI: 10.1029/2009JA015205

    Web of Science

    Scopus

  138. The predominant frequencies of the atmospheric perturbations and geomagnetic oscillations 査読有り

    M. Matsumura, T. Iyemori, M. Nose, M. Utsugi, Y. Odagi, Y. Tanaka, D. Han, N. Oshiman, H. Shinagawa, Y. Tabata

    Advances in Geosciences: Volume 21: Solar Terrestrial (ST)     頁: 129 - 142   2010年1月

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    記述言語:英語   掲載種別:論文集(書籍)内論文   出版者・発行元:World Scientific Publishing Co.  

    It has been expected that the atmospheric perturbation causes the acoustic resonance between the lower atmosphereand the thermosphere. The main resonance frequencies theoretically reported are around 3.7, 4.4-4.6 and 5.1-5.3mHz. We calculated mean power spectral densities and the occurrence rates of spectral peaks for the pressure perturbations and geomagnetic variations and found that the local maxima appeared in both data sets around the resonance frequencies. These maximaappear most clearly in August to October for pressure and in every season for geomagnetic fields. These results confirm the existence of the acoustic resonance coupling between the lower atmosphere and the ionosphere and suggest that the geomagnetic oscillations are frequently caused not only through magnetospheric plasma processes but also by lower atmospheric disturbances.

    DOI: 10.1142/9789812838209_0010

    Scopus

  139. 超高層物理学分野におけるメタデータ・データベースの構築

    小山幸伸, 河野貴久, 林寛生, 堀智昭, 田中良昌, 鍵谷将人, 吉田大紀, 上野悟, 阿部修司, 三好由純, 金田直樹, 能勢正仁, 岡田雅樹

    第2回データ工学と情報マネジメントに関するフォーラム論文集     頁: F4-3   2010年

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    記述言語:英語   掲載種別:研究論文(学術雑誌)  

  140. Response of ions of ionospheric origin to storm time substorms: Coordinated observations over the ionosphere and in the plasma sheet 査読有り

    M. Nose, S. Taguchi, S. P. Christon, M. R. Collier, T. E. Moore, C. W. Carlson, J. P. McFadden

    JOURNAL OF GEOPHYSICAL RESEARCH-SPACE PHYSICS   114 巻   2009年5月

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    記述言語:英語   掲載種別:研究論文(学術雑誌)   出版者・発行元:AMER GEOPHYSICAL UNION  

    We investigate variations of ion flux over the ionosphere and in the plasma sheet when storm time substorms are initiated, using simultaneous observations of neutral atoms in the energy range of up to a few keV measured by the low-energy neutral atom (LENA) imager on board the Imager for Magnetopause-to-Aurora Global Exploration ( IMAGE) satellite, outflowing ion flux of &lt;1 keV measured by the ion electrostatic analyzer (IESA) on board the Fast Auroral SnapshoT (FAST) satellite, and energetic (9-210 keV/e) ion flux measured by the energetic particle and ion composition (EPIC) instrument on board the Geotail satellite. We examined three storm intervals during which the IMAGE or FAST satellite was in a suitable location to observe ionospheric ion outflow and the Geotail satellite was in the plasma sheet on the nightside. The neutral atom flux observed by IMAGE/LENA in the first interval and outflowing ion flux observed by FAST/IESA in the second and third intervals indicate that storm time substorms can cause increases of low-energy ion flux over the ionosphere by a factor of 3-50 with time delay of less than several minutes. In the plasma sheet, the flux ratio of O+/H+ is rapidly enhanced at the storm time substorms and then increased gradually or stayed at a constant level in a time scale of similar to 1 h, suggesting a mass-dependent acceleration of ions at local dipolarization and a subsequent additional supply of O+ ions to the plasma sheet which have been extracted from the ionosphere at the substorms. These coordinated observations revealed that substorms have both an immediate effect and a delayed effect (i.e., two-step effect) on the ion composition in the plasma sheet.

    DOI: 10.1029/2009JA014048

    Web of Science

  141. Response of ions of ionospheric origin to storm time substorms: Coordinated observations over the ionosphere and in the plasma sheet 査読有り

    M. Nose, S. Taguchi, S. P. Christon, M. R. Collier, T. E. Moore, C. W. Carlson, J. P. McFadden

    JOURNAL OF GEOPHYSICAL RESEARCH-SPACE PHYSICS   114 巻 ( 5 )   2009年5月

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    記述言語:英語   掲載種別:研究論文(学術雑誌)   出版者・発行元:AMER GEOPHYSICAL UNION  

    We investigate variations of ion flux over the ionosphere and in the plasma sheet when storm time substorms are initiated, using simultaneous observations of neutral atoms in the energy range of up to a few keV measured by the low-energy neutral atom (LENA) imager on board the Imager for Magnetopause-to-Aurora Global Exploration ( IMAGE) satellite, outflowing ion flux of &lt;1 keV measured by the ion electrostatic analyzer (IESA) on board the Fast Auroral SnapshoT (FAST) satellite, and energetic (9-210 keV/e) ion flux measured by the energetic particle and ion composition (EPIC) instrument on board the Geotail satellite. We examined three storm intervals during which the IMAGE or FAST satellite was in a suitable location to observe ionospheric ion outflow and the Geotail satellite was in the plasma sheet on the nightside. The neutral atom flux observed by IMAGE/LENA in the first interval and outflowing ion flux observed by FAST/IESA in the second and third intervals indicate that storm time substorms can cause increases of low-energy ion flux over the ionosphere by a factor of 3-50 with time delay of less than several minutes. In the plasma sheet, the flux ratio of O+/H+ is rapidly enhanced at the storm time substorms and then increased gradually or stayed at a constant level in a time scale of similar to 1 h, suggesting a mass-dependent acceleration of ions at local dipolarization and a subsequent additional supply of O+ ions to the plasma sheet which have been extracted from the ionosphere at the substorms. These coordinated observations revealed that substorms have both an immediate effect and a delayed effect (i.e., two-step effect) on the ion composition in the plasma sheet.

    DOI: 10.1029/2009JA014048

    Web of Science

  142. Acoustic resonance between ground and thermosphere 査読有り

    M. Matsumura, T. Iyemori, Y. Tanaka, D. Han, M. Nose, M. Utsugi, N. Oshiman, H. Shinagawa, Y. Odagi, Y. Tabata

    Data Science Journal   8 巻   頁: S68 - S77   2009年3月

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    記述言語:英語   掲載種別:研究論文(学術雑誌)   出版者・発行元:Ubiquity Press Ltd  

    Ultra-low frequency acoustic waves called "acoustic gravity waves" or "infrasounds" are theoretically expected to resonate between the ground and the thermosphere. This resonance is a very important phenomenon causing the coupling of the solid Earth, neutral atmosphere, and ionospheric plasma. This acoustic resonance, however, has not been confirmed by direct observations. In this study, atmospheric perturbations on the ground and ionospheric disturbances were observed and compared with each other to confirm the existence of resonance. Atmospheric perturbations were observed with a barometer, and ionospheric disturbances were observed using the HF Doppler method. An end point of resonance is in the ionosphere, where conductivity is high and the dynamo effect occurs. Thus, geomagnetic observation is also useful, so the geomagnetic data were compared with other data. Power spectral density was calculated and averaged for each month. Peaks appeared at the theoretically expected resonance frequencies in the pressure and HF Doppler data. The frequencies of the peaks varied with the seasons. This is probably because the vertical temperature profile of the atmosphere varies with the seasons, as does the reflection height of infrasounds. These results indicate that acoustic resonance occurs frequently.

    DOI: 10.2481/dsj.8.S68

    Scopus

  143. Statistical visualization of the earth's magnetotail based on geotail data and the implied substorm model 査読有り

    Machida S., Miyashita Y., Ieda A., Nosé M., Nagata D., Liou K., Obara T., Nishida A., Saito Y., Mukai T.

    Annales Geophysicae   27 巻 ( 3 ) 頁: 1035 - 1046   2009年

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    記述言語:英語   掲載種別:研究論文(学術雑誌)   出版者・発行元:Annales Geophysicae  

    We investigated the temporal and spatial development of the near-Earth magnetotail during substorms based on multi-dimensional superposed-epoch analysis of Geotail data. The start time of the auroral break-up (t=0) of each substorm was determined from auroral data obtained by the Polar and IMAGE spacecraft. The key parameters derived from the plasma, magnetic-field, and electric-field data from Geotail were sorted by their meridional X(GSM)-Z(proxy) coordinates. The results show that the Poynting flux toward the plasmasheet center starts at least 10 min before the substorm onset, and is further enhanced at X̃-12RE (Earth radii) around 4 min before the onset. Simultaneously, large-amplitude fluctuations occurred, and earthward flows in the central plasma sheet between X̃-11RE and X̃-19R E and a duskward flow around X=-10RE were enhanced. The total pressure starts to decrease around X=-16RE about 4 min before the onset of the substorm. After the substorm onset, a notable dipolarization is observed and tailward lows commence, characterised by southward magnetic fields in the form of a plasmoid. We confirm various observable-parameter variations based on or predicted by the relevant substorm models; however, none of these can explain our results perfectly. Therefore, we propose a catapult (slingshot) current-sheet relaxation model, in which an earthward convective flow produced by catapult current-sheet relaxation and a converted duskward flow near the Earth are enhanced through flow braking around 4 min before the substorm onset. These flows induce a ballooning instability or other instabilities, causing the observed current disruption. The formation of the magnetic neutral line is a natural consequence of the present model, because the relaxation of a highly stretched catapult current-sheet produces a very thin current at its tailward edge being surrounded by intense earthward and tailward magnetic fields which were formerly the off-equatorial lobe magnetic fields. This location is the boundary between a highly stressed catapult current sheet and a Harris-type current sheet characterized by little stress. In addition, the flows induced around the boundary toward the current-sheet center may enhance the formation of the magnetic neutral line and the efficiency of magnetic reconnection. After magnetic reconnection is induced, it plays a significant role in driving the substorm. © Author(s) 2009.

    DOI: 10.5194/angeo-27-1035-2009

    Web of Science

    Scopus

  144. Determination of the substorm initiation region from a major conjunction interval of THEMIS satellites 査読有り

    Lui A. T. Y., Angelopoulos V., LeContel O., Frey H., Donovan E., Sibeck D. G., Liu W., Auster H. U., Larson D., Li X., Nose M., Fillingim M. O.

    JOURNAL OF GEOPHYSICAL RESEARCH-SPACE PHYSICS   113 巻   2008年12月

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    記述言語:日本語   掲載種別:研究論文(学術雑誌)  

    DOI: 10.1029/2008JA013424

    Web of Science

  145. Dawnside particle injection caused by sudden enhancement of solar wind dynamic pressure 査読有り

    Han D. -S., Yang H. -G., Nose M., Huang D. -H., Chen Z. -T., Hu H. -Q.

    JOURNAL OF ATMOSPHERIC AND SOLAR-TERRESTRIAL PHYSICS   70 巻 ( 16 ) 頁: 1995 - 1999   2008年12月

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    記述言語:日本語   掲載種別:研究論文(学術雑誌)  

    DOI: 10.1016/j.jastp.2008.07.019

    Web of Science

    J-GLOBAL

  146. Longitudinal association between magnetotail reconnection and auroral breakup based on Geotail and Polar observations 査読有り

    Ieda A., Fairfield D. H., Slavin J. A., Liou K., Meng C. -I., Machida S., Miyashita Y., Mukai T., Saito Y., Nose M., Shue J. -H., Parks G. K., Fillingim M. O.

    JOURNAL OF GEOPHYSICAL RESEARCH-SPACE PHYSICS   113 巻 ( 8 )   2008年8月

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    記述言語:英語   掲載種別:研究論文(学術雑誌)   出版者・発行元:Journal of Geophysical Research: Space Physics  

    The dawn-dusk locations of reconnection in the near-earth magnetotail at the time of isolated auroral breakup are studied to clarify whether breakup is always accompanied by reconnection. The near-earth reconnection is identified by tailward plasma flows faster than 200 km/s with southward magnetic field. We first identified 66 breakups in the Polar ultraviolet imager observations of the nightside polar ionosphere. We then studied tailward flows during breakups using Geotail in situ observations of the plasma sheet between 25 and 31 R E down the tail. It was found that the dawn-dusk (Y) locations of relatively fast (≥400 km/s) tailward flows were associated with breakup magnetic local time (MLT) by a regression line of YAGSM = -5.7 × (MLT + 0.6) RE with a correlation coefficient of 0.8. Most tailward flows were observed within 5 RE of the modeled Y locations, where tailward flows occurred in 88% of the 26 cases of breakups between 22 and 0 MLT. It is thus inferred that in most cases, breakup is accompanied by tailward flow near the breakup MLT with its dawn-dusk dimension ∼10 R E. There were only two events without tailward flows in the region where flows have been expected. These two events were an earthward flow event and a traveling compression region event, which are not inconsistent with the initiation of the near-earth reconnection. Auroral breakup is thus likely to always be accompanied by near-earth reconnection near breakup MLT. It is also inferred that reconnection and breakup occur simultaneously within a few minutes, assuming a time delay between reconnection onset and the arrival of tailward flows at satellite locations. Copyright 2008 by the American Geophysical Union.

    DOI: 10.1029/2008JA013127

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    Scopus

  147. Polarization analysis of a Pi2 pulsation using continuous wavelet transform 査読有り

    M. Kulesh, M. Nose, A. Holschneider, K. Yumoto

    EARTH PLANETS AND SPACE   59 巻 ( 8 ) 頁: 961 - 970   2007年

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    記述言語:英語   掲載種別:研究論文(学術雑誌)   出版者・発行元:TERRA SCIENTIFIC PUBL CO  

    In this contribution, we extend a series of previous works focused on an investigation of signal's polarization attributes using the continuous wavelet transform, where we proposed a method to map instantaneous polarization attributes of multicomponent signals in the wavelet domain and explicitly relate these attributes with the wavelet transform coefficients of the analyzed signal. In this work, we applied our polarization method to an examination of characteristics of Pi2 pulsations. We have shown some merits of the use of the continuous wavelet transform for the Pi2 pulsations' analysis. First, we used our polarization method for the geomagnetic field data from the MSR, KAK, GUA, SMA, BLM and LAQ observatories and showed some correlations between the polarization parameters of pulsation and the station's position (nightside or dayside). Secondly, we considered the signal's north components of a pair of stations and demonstrated a time-frequency variations of the phase difference between two stations during the pulsation.

    DOI: 10.1186/BF03352035

    Web of Science

    J-GLOBAL

  148. Realistic magnetospheric density model for 29 August 2000 査読有り

    Denton RE, Goldsten J, Lee DH, King RA, Dent ZC, Gallagher DL, Berube D, Takahashi K, Nose M, Milling D, Honary F

    JOURNAL OF ATMOSPHERIC AND SOLAR-TERRESTRIAL PHYSICS   68 巻 ( 6 ) 頁: 615 - 628   2006年3月

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    記述言語:日本語   掲載種別:研究論文(学術雑誌)  

    DOI: 10.1016/j.jastp.2005.11.009

    Web of Science

    J-GLOBAL

  149. ERG - A small-satellite mission to investigate the dynamics of the inner magnetosphere

    Shlokawa K., Seki K., Miyoshi Y., Leda A., Ono T., Iizima M., Nagatsuma T., Obara T., Takashima T., Asamura K., Kasaba Y., Matsuoka A., Saito Y., Saito H., Hirahara M., Tonegawa Y., Toyama F., Tanaka M., Nose M., Kasahara Y., Yumoto K., Kawano H., Yoshikawa A., Ebihara Y., Yukimatsu A., Sato N., Watanabe S.

    ADVANCES IN SPACE RESEARCH   38 巻 ( 8 ) 頁: 1861 - 1869   2006年

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    記述言語:英語   掲載種別:研究論文(学術雑誌)  

    DOI: 10.1016/j.asr.2005.05.089

    Web of Science

    Scopus

  150. 'Cosmic-ray-mediated' interplanetary shocks in 1994 and 2003 査読有り

    T. Terasawa, M. Oka, K. Nakata, K. Keika, M. Nose, R. W. McEntire, Y. Saito, T. Mukai

    PARTICLE ACCELERATION, SPACE PLASMA PHYSICS, SOLAR RADIATION AND THE EARTH'S ATMOSPHERE AND CLIMATE   37 巻 ( 8 ) 頁: 1408 - 1412   2006年

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    記述言語:英語   掲載種別:研究論文(学術雑誌)   出版者・発行元:ELSEVIER SCIENCE LTD  

    Shock accelerated nonthermal particles are thought to contribute to modify the shock structure. Here we present two such cases at two strong interplanetary shocks in 1994 and 2003, and try to see how the nonlinear feature depend on the shock parameters, such as Mach number and shock angle. (c) 2006 COSPAR. Published by Elsevier Ltd. All rights reserved.

    DOI: 10.1016/j.asr.2006.03.012

    Web of Science

  151. Longitudinal dependence of characteristics of low-latitude Pi2 pulsations observed at Kakioka and Hermanus 査読有り

    M Nose, K Liou, PR Sutcliffe

    EARTH PLANETS AND SPACE   58 巻 ( 6 ) 頁: 775 - 783   2006年

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    記述言語:英語   掲載種別:研究論文(学術雑誌)   出版者・発行元:TERRA SCIENTIFIC PUBL CO  

    We statistically investigated longitudinal dependence of characteristics of low-latitude Pi2 pulsations to find the longitudinal structure of the plasmaspheric cavity mode. We used the geomagnetic field data from two ground stations, Kakioka (27.2 degrees geomagnetic latitude, 208.5 degrees geomagnetic longitude) and Hermanus (-33.9 degrees geomagnetic latitude, 82.2 degrees geomagnetic longitude), and auroral image data acquired by the ultraviolet imager onboard the Polar satellite for the period of December 4, 1996 to March 3, 1997. Our findings include the following: (1) Pi2 amplitude is the largest around the magnetic local time of the auroral breakup site and decreases away from it; (2) when a nightside Pi2 pulsation has large amplitude, a dayside Pi2 pulsation can be observed with a similar waveform; (3) Pi2 pulsations generally have no clear phase differences (mean phase difference of 3.3 degrees) between Kakioka and Hermanus, except for some events; and (4) the phase difference is independent on Delta MLT (difference of magnetic local time between a station and the auroral breakup). These observations suggest that the plasmaspheric cavity mode can be excited globally with a very small value of the azimuthal wave number (m approximate to 0).

    DOI: 10.1186/BF03351981

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    J-GLOBAL

  152. Simultaneous observations of ions of ionospheric orgin over the ionosphere and in the plasma sheet at storm-time substorms

    Nosé, M, T. Kunori, Y. Ono, S. Taguchi, K. Hosokawa, T. E. Moore, M. R. Collier, S. P. Christon, E. W. McEntire

    Proceedings of the Eighth International Conference on Substorms     頁: 203 - 208   2006年

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    記述言語:英語   掲載種別:研究論文(国際会議プロシーディングス)  

  153. Geotail observations of signatures in the near-Earth magnetotail for the extremely intense substorms of the 30 October 2003 storm 査読有り

    Miyashita Y, Miyoshi Y, Matsumoto Y, Ieda A, Kamide Y, Nose M, Machida S, Hayakawa H, McEntire RW, Christon SP, Evans DS, Troshichev OA

    JOURNAL OF GEOPHYSICAL RESEARCH-SPACE PHYSICS   110 巻 ( 9 )   2005年

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    記述言語:英語   掲載種別:研究論文(学術雑誌)   出版者・発行元:Journal of Geophysical Research: Space Physics  

    Two coronal mass ejections associated with the X17 and X10 solar flares reached the Earth's environment at very high speeds on 29 and 30 October 2003, respectively, causing very intense geomagnetic storms (Dst ∼ -400 nT). The present study focused on the main phase of the 30 October storm during which the Geotail spacecraft was within the near-Earth magnetotail at X∼ -8 R E. A number of extremely intense substorms occurred during this period. In one of them, the intensity of the westward auroral electrojet exceeded 3000 nT, which was one of the largest magnitudes ever observed. The energetic particle observations from the low-altitude, polar-orbiting NOAA satellites indicate that the auroral oval shifted equatorward to magnetic latitudes much lower than usual, as low as 50°. Throughout the interval, the magnetic field in the near-Earth magnetotail, and'possibly the plasma density, was much larger than usual, indicating a considerable degree of energy accumulation in the lobe region and compression of the plasma sheet and very intense crosstail currents. The dense plasma may be responsible for the intense auroral electrojet and the intense ring current. Very large, rapid dipolarizations occurred in relation to the intense substorms. High-energy particle fluxes were an order of magnitude higher than usual, and their increases took place immediately after the dipolarizations. Fast tailward flows with large southward magnetic fields as well as fluxes of energetic heavy ions (oxygen) were also observed, suggesting that the magnetic reconnection took place in the near-Earth magnetotail, associated with the very intense substorms. This location is much closer to the Earth than usual, probably as close to the Earth as ever reported. These magnetotail and auroral observations as well as other results reported previously suggest that the entire magnetosphere was considerably distorted during the storm. Copyright 2005 by the American Geophysical Union.

    DOI: 10.1029/2005JA011070

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  154. Comparison of energetic ion composition between ring current and plasma sheet 査読有り

    M Nose, RW McEntire, SP Christon

    Frontiers in Magnetospheric Plasma Physics: Celebrating 10 Years of Geotail Operation   16 巻 ( C ) 頁: 198 - 202   2005年

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    記述言語:英語   掲載種別:研究論文(国際会議プロシーディングス)   出版者・発行元:ELSEVIER SCIENCE BV  

    We calculated the energy density of H+, He+, and O+ ions in the plasma sheet during the development of a magnetic storm, using energetic (9-210 keV) particle flux data obtained by the suprathermal ion composition spectrometer (STICS) sensor of the energetic particle and ion composition (EPIC) instrument on the Geotail spacecraft. We found that the energy density ratio of O+/H+ stayed at similar to 0.1 before storms, but increased as storms developed, reaching 0.5-1.0 at a peak of storms. The energy density ratio of He+/H+ was rather constant at 0.01-0.02. These results are comparable with those in the outer ring current reported by the previous studies. This implies that the ions of ionospheric origin (O+ and He+) are transported to the ring current through the plasma sheet.

    DOI: 10.1016/S0964-2749(05)80031-9

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  155. Geomagnetic activity dependence of occurrence probability and spatial distribution of upstream events 査読有り

    K Keika, M Nose, SP Christon, RW McEntire

    Frontiers in Magnetospheric Plasma Physics: Celebrating 10 Years of Geotail Operation   16 巻 ( C ) 頁: 297 - 300   2005年

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    記述言語:英語   掲載種別:研究論文(国際会議プロシーディングス)   出版者・発行元:ELSEVIER SCIENCE BV  

    We investigated upstream events observed by the ion composition system (ICS) sensor of the energetic particles and ion composition (EPIC) instrument on board the Geotail spacecraft. We examined how occurrence probability and spatial distribution of upstream events depend on the geomagnetic activity. The results showed that the upstream events were observed more frequently in the dawn side during intense geomagnetic activity in particular. We also analyzed carbon-nitrogen-oxygen ions during the upstream events. From the above results we discuss origin of the upstream energetic ions.

    DOI: 10.1016/S0964-2749(05)80045-9

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  156. Source of Pc4 pulsations observed on the nightside 査読有り

    Takahashi K, Liou K, Yumoto K, Kitamura K, Nose M, Honary F

    JOURNAL OF GEOPHYSICAL RESEARCH-SPACE PHYSICS   110 巻 ( 12 )   2005年

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    記述言語:英語   掲載種別:研究論文(学術雑誌)  

    DOI: 10.1029/2005JA011093

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  157. Influence of solar wind on source of ring current plasma 査読有り

    M Nose, RW McEntire, SP Christon

    Frontiers in Magnetospheric Plasma Physics: Celebrating 10 Years of Geotail Operation   16 巻 ( C ) 頁: 48 - 53   2005年

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    記述言語:英語   掲載種別:研究論文(国際会議プロシーディングス)   出版者・発行元:ELSEVIER SCIENCE BV  

    In the present study we aim to derive empirical equations relating source plasma of the ring current to the solar wind. We used the energy spectra at energies of 9-135 keV obtained by the suprathermal ion composition spectrometer (STICS) sensor of the energetic particle and ion composition (EPIC) instrument on the Geotail spacecraft. The plasma parameters (i.e., number density and temperature) of H+, O+, and He were estimated by fitting the K-distribution function to the energy spectra in the region of a geocentric distance of 8.5-10.5 RE and magnetic local time of 2200-0200 hour. The results showed that the H+ number density in the plasma sheet correlated with the solar wind density, while the O+ and He+ number density had no correlation with the solar wind parameters. Thus the origin of H+ ions in the plasma sheet is thought to be the solar wind. O+ and He+ ions in the plasma sheet are expected to have different origin from the solar wind. It was also found that the temperature of H+, O+ and He+ has a good correlation with the solar wind velocity and that gradients of the derived empirical equations can be ordered by ion mass. This implies that ions are accelerated in a mass-dependent way.

    DOI: 10.1016/S0964-2749(05)80009-5

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  158. Dynamics of ions of ionospheric origin during magnetic storms: Their acceleration mechanism and transport path to ring current 査読有り

    M. Nosé, K. Takahashi, S. Ohtani, S. P. Christon, R. W. McEntire

    Geophysical Monograph Series   155 巻   頁: 61 - 71   2005年

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    記述言語:英語   掲載種別:論文集(書籍)内論文   出版者・発行元:Blackwell Publishing Ltd  

    We investigated the spatial and temporal properties of the 9-210 keV/e ion composition in the near-Earth plasma sheet (at geocentric distance, r, of 8-15 RE), using energetic ion flux data acquired by the suprathermal ion composition spectrometer (STICS) sensor of the energetic particle and ion composition (EPIC) instrument onboard the Geotail spacecraft. We analyzed data covering 8.3 years to find the MLT-r distribution of the H+, He+, and O+ energy densities (as well as the He+/H+ and 0+/H+energy density ratios) as a function of the SYM-H index. We obtained the following results: (1) The energy density increases as SYM-H decreases
    (2) The energy density change depends on ion mass: the largest change occurs in 0+, and the smallest change occurs in H+ (3) The energy density shows a dawn-dusk asymmetry when SYM-H &lt
    - 5 0 nT, being larger on the duskside than on the dawnside
    and (4) The He+/H+and 0+/H+ energy density ratios in the plasma sheet are similar to those in the ring current. From these results we conclude that ionospheric He+ and O+ ions are transported to the plasma sheet, accelerated there by the dawn-to-dusk electric field in a mass-dependent manner (heavier ions gain more energy than lighter ions), and injected into the ring current region. Both the ion flux from the ionosphere and the energy gain in the plasma sheet become large when the geomagnetic disturbance becomes intense.

    DOI: 10.1029/155GM08

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  159. Acceleration sites of energetic ions upstream of the Earth's bow shock and in the magnetosheath: Statistical study on charge states of heavy ions 査読有り

    Keika K, Nose M, Christon SP, McEntire RW

    JOURNAL OF GEOPHYSICAL RESEARCH-SPACE PHYSICS   109 巻 ( A11 )   2004年11月

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    記述言語:英語   掲載種別:研究論文(学術雑誌)  

    DOI: 10.1029/2003JA009953

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  160. A comparative analysis of low-latitude Pi2 pulsations observed by Ørsted and ground stations 査読有り

    D.-S. Han, T. Iyemori, M. Nosé, H. McCreadie, Y. Gao, F. Yang, S. Yamashita, P. Stauning

    Journal of Geophysical Research A: Space Physics   109 巻 ( 10 )   2004年

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    記述言語:英語   掲載種別:研究論文(学術雑誌)  

    DOI: 10.1029/2004JA010576

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  161. Change of the plasma sheet ion composition during magnetic storm development observed by the Geotail spacecraft 査読有り

    M Nose, RW McEntire, SP Christon

    JOURNAL OF GEOPHYSICAL RESEARCH-SPACE PHYSICS   108 巻 ( A5 )   2003年5月

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    記述言語:英語   掲載種別:研究論文(学術雑誌)   出版者・発行元:AMER GEOPHYSICAL UNION  

    [1] The present study aims to investigate how and where ions of ionospheric origin are accelerated to the ring current energy (a few tens to a few hundreds of keV) and how they are supplied to the ring current. We examined the plasma sheet ion composition during magnetic storm development, using energetic (9-210 keV) ion flux data obtained by the suprathermal ion composition spectrometer (STICS) sensor of the energetic particle and ion composition (EPIC) instrument on board the Geotail spacecraft. We selected two magnetic storms, that is, the 16-17 May 2000 storm and the 25 December 1998 storm, for which the energy density ratios of O+/H+ and He+/H+ in the plasma sheet were calculated from the EPIC/STICS data. These magnetic storms had a minimum of the SYM-H index (the 1-min Dst index) less than -50 nT and a duration of the main phase shorter than 6 hours. We obtained the following results: (1) Both the O+/H+ and He+/H+ energy density ratios were anticorrelated with the SYM-H index (\r\ = 0.73-0.88); (2) The O+ /H+ energy density ratio was rather constant at similar to0.1 before storms, but reached 0.3-1.0 at the storm maximum; and (3) The He+ /H+ energy density ratio increased from 0.01-0.02 before storms to 0.04-0.1 at the storm maximum. These ion composition changes are comparable to those in the ring current, which have been reported by previous studies, indicating that ions of ionospheric origin are possibly convected to the ring current via the plasma sheet. A close inspection of ion energy spectra revealed that the observed ion composition changes can be attributed to the mass-dependent acceleration of ions by the dawn-to-dusk electric field in the current sheet and the additional transport of ionospheric ions into the plasma sheet.

    DOI: 10.1029/2002JA009660

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  162. Local time dependence of the frequency of Pi2 waves simultaneously observed at 5 low-latitude stations 査読有り

    DS Han, T Iyemori, YF Gao, YH Sano, FX Yang, WS Li, M Nose

    EARTH PLANETS AND SPACE   55 巻 ( 10 ) 頁: 601 - 612   2003年

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    記述言語:英語   掲載種別:研究論文(学術雑誌)   出版者・発行元:TERRA SCIENTIFIC PUBL CO  

    One-second resolution geomagnetic data from 5 stations located at low-latitudes (i.e., L = 1.2 similar to 1.6) were used to examine the local time dependence of the dominant frequency of Pi2 pulsations. We analyzed 183 Pi2 events simultaneously recorded at the 5 stations and discussed their possible generation mechanisms. The averaged dominant frequency of the H (horizontal) component is higher on the dawn side than that on the dusk side and shows a peak value in the post-midnight at around 03 LT, which confirms the LT dependence previously suggested from single station data (i.e., non-simultaneous observation). However, some of the events have no LT dependence. For the events which show the LT dependence at low-latitudes, we infer that the cavity resonance mode is a plausible generation mechanism, but we do not rule out the possibility of the plasmaspheric surface wave mode which has also been suggested. For the events having a common frequency between the eastern and western stations, we suggest the cavity resonance mode to be the mechanism. The averaged dominant frequency of the D component does not show any clear LT dependence, and only about 20% of Pi2s have identical frequency for both the H and D components, therefore we suggest that the H and D oscillations of Pi2s are generated from different mechanisms. We also found that the frequency of different parts of a Pi2 pulsation, i.e., the dominant frequency for leading part and trailing part of the pulsation, is different, and the frequency of the trailing part is lower than that of the leading part.

    DOI: 10.1186/BF03352467

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  163. Local time dependence of the dominant frequency of Pi2 pulsations at mid- and low-latitudes 査読有り

    K Kosaka, T Iyemori, M Nose, M Bitterly, J Bitterly

    EARTH PLANETS AND SPACE   54 巻 ( 7 ) 頁: 771 - 781   2002年

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    記述言語:英語   掲載種別:研究論文(学術雑誌)   出版者・発行元:TERRA SCIENTIFIC PUBL CO  

    We carried out a statistical analysis of Pit pulsations using the geomagnetic field data obtained at three ground stations. A local time dependence of the dominant frequency of Pit was found on the nightside. The frequency of mid-latitude Pit pulsations is lower on the dusk side than that on the dawn side. This tendency is attributed to the shape of the plasmasphere which bulges out to the dusk side. It was confirmed that the Pit frequency depends also on the geomagnetic activity measured with Kp index. During the disturbed periods, Pit pulsations have higher frequency than that in the quiet periods. This dependence is interpreted to be caused by the size of the plasmapause which is smaller under the disturbed conditions than that under the quiet conditions. The dominant frequency of Pit pulsations at lower latitudes has a peak in post-midnight, and a Kp dependence similar to that at mid-latitudes is also observed. However, the result for low-latitude Pit's is different from that for mid-latitude Pit. We consider that the dominant mechanism of mid-latitude Pit is the plasmaspheric surface wave. In order to examine the idea that the surface wave on the plasmapause is the dominant mechanism of Pit pulsations at mid-latitudes, we estimated the resonance frequency of the surface wave on the plasmapause using a plasmaspheric model which includes the effect of the plasmaspheric bulge. The estimated frequency of the surface wave is higher on the dawn side than that on the dusk side, which is essentially consistent with the observational results. The predicted frequency under quiet conditions (Kp less than or equal to 3) is nearly equal to the observed Pit frequency at mid-latitudes. These results suggest that the dominant frequency of Pit pulsations at mid-latitudes depends on the structure of the plasmapause.

    DOI: 10.1186/BF03351730

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  164. Storm-substorm relationship: Contribution of the tail current to Dst

    Ohtani S.

    Journal of Geophysical Research: Space Physics   106 巻 ( A10 ) 頁: 21199 - 21209   2001年10月

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    記述言語:英語   掲載種別:研究論文(学術雑誌)   出版者・発行元:Journal of Geophysical Research: Space Physics  

    DOI: 10.1029/2000ja000400

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  165. Storm-substorm relationship: Contribution of the tail current to Dst 査読有り

    S Ohtani, M Nose, G Rostoker, H Singer, ATY Lui, M Nakamura

    JOURNAL OF GEOPHYSICAL RESEARCH-SPACE PHYSICS   106 巻 ( A10 ) 頁: 21199 - 21209   2001年10月

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    記述言語:英語   掲載種別:研究論文(学術雑誌)   出版者・発行元:AMER GEOPHYSICAL UNION  

    The Dst index has been conventionally used as a measure of the storm intensity, which ideally assumes that the associated ground magnetic disturbance is caused by the ring current. The present study examines the contribution of the tail current to Dst, focusing on the occurrence of geosynchronous dipolarization close to the Dst minimum, in other words, the start of the storm recovery phase. The Sym-H (referred to as Dst((Sy-H)) hereafter) index rather than the conventional Dst index is used because of its higher time resolution (1 min). For the June 1998 storm event, dipolarization started at two GOES satellites and the Geotail satellite in the near-Earth tail when Dst((Sym-H)) reached its minimum. This result indicates that the source current was located outside of geosynchronous orbit, and therefore the recovery of Dst((Sym-H)) can be attributed to the reduction of the tail current rather than the decay of the ring current. A statistical study based on 59 storm events (79 GOES events) confirms the tendency for geosynchronous magnetic field to dipolarize at the Dst((Sym-H)) minimum. It is therefore highly likely that the Dst((Sym-H)) minimum is misidentified as the start of the ring current (storm) decay at a time when the ring current may actually be intensifying owing to substorm-associated injection, From the magnitude of the Dst((Sym-H)) recovery during the interval of geosynchronous dipolarization, the contribution of the tail current to Dst((Sym-H)) at the Dst((Sym-H)) minimum is estimated to be 20-25%. However, the contribution of the tail current may be even larger because the tail current may not return to preintensification levels and may continue to contribute to Dst(sym-fn after dipolarization. The trigger of dipolarization (substorm) and the subsequent recovery of Dst((Sym-H)) tend to take place in the course of the reduction of the southward interplanetary magnetic field (IMF) B-Z. It is therefore suggested that the ring current (storm) recovers after the substorm since the magnetospheric convection weakens because of weaker southward IMF B-Z.

    DOI: 10.1029/2000JA000400

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  166. Ion composition of the near-Earth plasma sheet in storm and quiet intervals: Geotail/EPIC measurements 査読有り

    M Nose, S Ohtani, K Takahashi, ATY Lui, RW McEntire, DJ Williams, SP Christon, K Yumoto

    JOURNAL OF GEOPHYSICAL RESEARCH-SPACE PHYSICS   106 巻 ( A5 ) 頁: 8391 - 8403   2001年5月

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    記述言語:英語   掲載種別:研究論文(学術雑誌)   出版者・発行元:AMER GEOPHYSICAL UNION  

    We investigate the ion composition of the near-Earth plasma sheet in storm and quiet intervals, using energetic (9-210 keV) particle flux data obtained by the suprathermal ion composition spectrometer (STICS) sensor of the energetic particle and ion composition (EPIC) instrument on the Geotail spacecraft. In 1998 four magnetic storms (minimum Dst &lt; -50 nT) occurred when Geotail was located in the near-Earth plasma sheet (X greater than or equal to -10 R-E) For each of the storms, we have selected a col responding quiet interval from time periods when Geotail revisited the near-Earth plasma. sheet under the condition Dst &gt; -20 nT, The energy density of the H+, He+, and O+ ions was computed from the EPIC/STICS data for these storm and quiet-time events. We obtained. the following results: (1) The energy density is higher during storms than during quiet times for all ion species (H+, He+, and O+); (2) the He+/H+ energy density ratio during storms is 0.01-0.02, while that, during quiet times is similar to0.01; and (3) the O+/H+ energy density ratio is significantly larger during storms (0.2-0.6) than during quiet times (0.05-0.1). To explain these results we suggested a current sheet acceleration mechanism in which ions are energized by the dawn-to-dusk convection electric field in a mass-dependent way in the course of interaction with the current sheet.

    DOI: 10.1029/2000JA000376

    DOI: 10.1029/2000ja000376

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  167. Composition of energetic neutral atoms during a storm main phase 査読有り

    ATY Lui, RW McEntire, M Nose, DJ Williams

    GEOPHYSICAL RESEARCH LETTERS   28 巻 ( 7 ) 頁: 1363 - 1366   2001年4月

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    記述言語:英語   掲載種別:研究論文(学術雑誌)   出版者・発行元:AMER GEOPHYSICAL UNION  

    The first composition observation of energetic neutral atom (ENA) emissions during the main phase of a geomagnetic storm is reported here. The measurements were made by the Energetic Particles and Ion Composition (EPIC) instrument on the Geotail on October 22, 1999 when the ring current was strengthening. For this geomagnetic storm, while the Dst index was monotonically decreasing during the main phase, ENA fluxes showed two major enhancements with distinctly different temporal profiles. For the first enhancement, the increases in ENA fluxes were rapid and the subsequent evolution was species dependent. Both the integral ENA (E &gt;similar to 12 keV) and neutral hydrogen (E &gt; 67 keV) fluxes remained relatively unchanged after the increase while the neutral oxygen (E &gt; 203 keV) fluxes decreased rapidly. For the second enhancement, the increases in ENA fluxes of all species were rather gradual and the subsequent decrease in the neutral oxygen flux was also slow. The slow decrease may be related to the continual AE enhancement during that time. For total energies above 200 keV, the intensity of ENA oxygen was the highest, followed by hydrogen, and then by helium. This ordering of ENA intensity for these species is similar to the previous ENA composition results obtained for the recovery phase of another geomagnetic storm.

    DOI: 10.1029/2000GL012612

    DOI: 10.1029/2000gl012612

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  168. Convection enhancements in the low-latitude lobe for substorm onset 査読有り

    S Taguchi, M Kiyohara, T Mukai, M Nose, Y Saito

    JOURNAL OF GEOPHYSICAL RESEARCH-SPACE PHYSICS   106 巻 ( A3 ) 頁: 3943 - 3952   2001年3月

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    記述言語:英語   掲載種別:研究論文(学術雑誌)   出版者・発行元:AMER GEOPHYSICAL UNION  

    Characteristics of the lobe plasma convection enhancements around Pi2 substorm onset have been clarified with Geotail data. We identified 92 lobe substorm onset events within 5 R-E from an estimated neutral sheet from X = -10 to -35 R-E, and we found 27 convection enhancement events. These events were categorized into two types depending on whether the magnetic field tilts northward or southward in coincidence with intensity. decrease. The former type was identified in 12 of the 27 and found to be generally at shorter distances from the Earth than the latter, The frequencies of the lobe observations in the above Z width are small (less than or equal to 11%); that is, the plasma sheet usually occurs. In this situation, 80%: of the 27 are identified only within 2.5 R-E from the estimated neutral sheet. This indicates that the convection enhancement events occur. in association with the lobe appearance in the vicinity of the neutral sheet. This is also recognized in the X-Y distribution of the lon-latitude lobe observation; the relatively high frequencies of greater than or equal to4% which have a dawn-dusk asymmetry roughly correspond to the event location. Examination of the convection speed shows that the peak lies in 0.04V(A) to 0.1V(A) (V-A is the local Alfven velocity) and that the duration is 1 - 3 min for most cases. Identification probability of the convection enhancement events nas also examined. Both types of events have very similar occurrence probability in Y = 0-10 R-E, which is consistent with an interpretation that both are created by a common process, i,e,, lobe reconnection in the near-Earth neutral line (NENL). For the downside of this Y region, however, the southward field tilting type more often appears than he other, implying that the convection enhancements occur in an asymmetric manner with respect to the NENL.

    DOI: 10.1029/2000JA900097

    DOI: 10.1029/2000ja900097

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  169. Change of energetic ion composition in the plasma sheet during substorms 査読有り

    M Nose, S Ohtani, ATY Lui, SP Christon, RW McEntire, DJ Williams, T Mukai, Y Saito, K Yumoto

    JOURNAL OF GEOPHYSICAL RESEARCH-SPACE PHYSICS   105 巻 ( A10 ) 頁: 23277 - 23286   2000年10月

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    記述言語:英語   掲載種別:研究論文(学術雑誌)   出版者・発行元:AMER GEOPHYSICAL UNION  

    It I-las been reported by previous studies that the energetic particle flux of ions of ionospheric origin like O+ ions is more enhanced than that of Hf ions in the near-Earth tail (X similar to-6 to -16 R-E) during substorms. To explain this strong O+ flux enhancement, some studies have surmised that thermal O+ ions in the plasma sheet boundary layer or the lobe are strongly accelerated at the magnetic reconnection region (X similar to-20 to -30 R-E), and are subsequently transported into the near-Earth plasma sheet; with earthward plasma flows. However, other studies have supposed that the strong O+ flux enhancement is caused by local magnetic field reconfiguration (local dipolarization). In the present study, we used Geotail/EPIC measurements of energetic (60 keV to 3.6 MeV) ion flux to test the above two scenarios. We investigated ion composition in the plasma sheet while earthward plasma flows and/or dipolarization signatures were observed. In terms of energy density ratio of oxygen ions to protons, the observational results can be summarized as follows: (1) earthward plasma flows without dipolarization signatures did not accompany large increases of the ratio in most cases; (2) when earthward plasma flows appeared with dipolarization signatures, they accompanied increases of the ratio; and (3) most of dipolarization events were associated with large increases of the ratio. These results suggest that the strong increase in the energetic oxygen constituent in the near-Earth plasma sheet is due to acceleration of ions during dipolarization, consistent with the latter scenario.

    DOI: 10.1029/2000JA000129

    DOI: 10.1029/2000ja000129

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  170. Acceleration of oxygen ions of ionospheric origin in the near-Earth magnetotail during substorms 査読有り

    M Nose, ATY Lui, S Ohtani, BH Mauk, RW McEntire, DJ Williams, T Mukai, K Yumoto

    JOURNAL OF GEOPHYSICAL RESEARCH-SPACE PHYSICS   105 巻 ( A4 ) 頁: 7669 - 7677   2000年4月

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    記述言語:英語   掲載種別:研究論文(学術雑誌)   出版者・発行元:AMER GEOPHYSICAL UNION  

    Measurements from the suprathermal ion composition spectrometer (STICS) sensor of the energetic particle and ion composition (EPIC) instrument on the Geotail spacecraft were used to investigate dynamics of O+ ions of ionospheric origin at energies of 9 keV to 210 keV in the near-Earth plasma, sheet during the substorm expansion phase. Substorm signatures were clearly observed on the ground at 1850 UT on May 17, 1995. In the expansion phase of this substorm, Geotail stayed in the plasma sheet at X similar to-10.5 R-E and observed a local dipolarization signature accompanied by strong disturbances of the magnetic field. From the energetic ion flux data of EPIC/STICS, we obtained the following results: (1) energetic flux enhancement was more pronounced for O+ than for H+; (2) the flux was enhanced almost simultaneously with local dipolarization; (3) the enhancement factor of O+ ions (EO+), which represents the enhancement of the O+ flux ratio (after and before substorm onset) relative to the H+ flux ratio, was Bs large as 1.31; and (4) thermal energy increased from 8.9 keV to 42.8 keV for O+ ions and from 9.4 keV to 15.9 keV for H+ ions. We also performed statistical analysis for 35 events of local dipolarization found in the near-Earth region (X similar to-6 to -16 R-E). We found that EO+ is larger than unity in all ranges of radial distance and that the average value of EO+ is 1.37. These results suggest that O+ ions are commonly more energized than H+ ions during the substorm expansion phase. To interpret these observational results, we propose a mechanism in which ions are accelerated in a non-adiabatic way during substorm-associated field reconfiguration.

    DOI: 10.1029/1999JA000318

    DOI: 10.1029/1999ja000318

    Web of Science

  171. Automated detection of Pi 2 pulsations using wavelet analysis: 2. An application for dayside Pi 2 pulsation study 査読有り

    M Nose

    EARTH PLANETS AND SPACE   51 巻 ( 1 ) 頁: 23 - 32   1999年

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    記述言語:英語   掲載種別:研究論文(学術雑誌)   出版者・発行元:TERRA SCIENTIFIC PUBL CO  

    We investigated statistical characteristics of dayside Pi 2 pulsations observed at Mineyama (25.5 degrees geomagnetic latitude) from November 1994 through June 1996, using an algorithm to detect Pi 2 pulsations which was introduced in Part I of the accompanying paper. We obtained the following results. (1) The ratio of the number of Pi 2 pulsations on the dayside (06-18 MLT) to that on the nightside (18-06 MLT) was about 31%. (2) The polarization of the dayside Pi 2 pulsations changed from right-handed before local noon to left-handed after local noon. (3) Wave power of dayside Pi 2 pulsations in the H-component has a peak around local noon and dips on both dawn and dusk sides. (4) Frequency of the fundamental wave is ranging from 9 mHz to 30 mHz with dominant frequency of 17-24 mHz, and frequency ratios of the first three harmonics are 1 : (1.7 +/- 0.5) : (2.3 +/- 0.7). We found that the magnetospheric cavity model can explain most of these observational results.

    DOI: 10.1186/BF03352206

    Web of Science

    J-GLOBAL

  172. Temporal relationship between midtail traveling compression regions and substorm onset: Evidence for near-Earth neutral line formation in the late growth phase 査読有り

    S Taguchi, JA Slavin, M Kiyohara, M Nose, GD Reeves, RP Lepping

    JOURNAL OF GEOPHYSICAL RESEARCH-SPACE PHYSICS   103 巻 ( A11 ) 頁: 26607 - 26612   1998年11月

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    記述言語:英語   掲載種別:研究論文(学術雑誌)   出版者・発行元:AMER GEOPHYSICAL UNION  

    The timing of the near-Earth neutral line (NENL) formation relative to substorm onset signatures has been a central debate in substorm research for some time. Several recent studies have suggested that the direct identification of the reconnection site, at least in its initial stage, is difficult because it may be a very limited region spatially. Our approach to this timing problem is the examination of the midtail lobe traveling compression regions (TCRs) relative to onset during substorm events. Fifty-nine midtail TCRs in the IMP 8 magnetotail observations are analyzed. These midtail TCRs differ from the distant tail TCRs in that they lack the first half of the north and south tilting of the field during the compression. The flat B-Z phase preceding the south tilting interval in these midtail compression regions has been interpreted as being due to the close proximity to the growing plasmoid bulge just prior to plasmoid ejection down the tail. The results of our analysis show that these TCRs start a few minutes before or simultaneously (accuracy of 1 min) with Pi2 onset at low-latitude or midlatitude ground stations and the particle injection at the geosynchronous orbit. Before the plasmoid bulge formation starts, the NENL must start to form in the plasma sheet; that is, the formation of NENL must initially occur on closed field lines to form the plasmoids which compress the lobes to cause the TCRs. Our results support this view and allow us to conclude that NENL forms before ground and geosynchronous substorm onset signatures, i.e., in the late growth phase. The implications of these results for magnetospheric substorm models are discussed.

    DOI: 10.1029/98JA02617

    DOI: 10.1029/98ja02617

    Web of Science

  173. Electron precipitation accompanying Pc 5 pulsations observed by the DE satellites and at a ground station 査読有り

    M Nose, T Iyemori, M Sugiura, JA Slavin, RA Hoffman, JD Winningham, N Sato

    JOURNAL OF GEOPHYSICAL RESEARCH-SPACE PHYSICS   103 巻 ( A8 ) 頁: 17587 - 17604   1998年8月

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    記述言語:英語   掲載種別:研究論文(学術雑誌)   出版者・発行元:AMER GEOPHYSICAL UNION  

    Using data from the polar orbiting Dynamic Explorer (DE) -1 and -2 satellites and a ground-based station, we investigated electron precipitation phenomena accompanying Pc 5 pulsations. DE-2 observed oscillatory disturbances in the magnetic and electric fields in the upper ionosphere at the geomagnetic footprint of the high altitude region in which transverse Pc 5 pulsations were detected by DE-1. DE-2 observed electrons precipitating into the ionosphere with energies of several keV to several tens of keV, These electrons were accelerated in the direction of the ambient magnetic field. When Pc 5 pulsations in the H-component and periodic variations of cosmic radio noise absorption (CNA pulsations) were observed at Syowa Station, DE-2 which was in geomagnetic conjunction with Syowa Station also observed oscillatory disturbances in the magnetic and electric fields. These oscillatory disturbances are caused by small-scale field-aligned currents each with. width of 0.5 degrees-1.4 degrees invariant latitude. This suggests that Pc 5 pulsations have a small-scale resonance structure in the radial direction. The resonance structure has a small scale comparable to the ion acoustic gyroradius, then kinetic Alfven waves having electric fields parallel to the ambient magnetic field can arise. The parallel electric field generates a field-aligned potential drop of about 3-5 kV. Electrons accelerated by these kinetic Alfven waves would cause CNA pulsations, the phase of which leads that of the B-component of the Pc 5 pulsations by 90 degrees in the southern hemisphere. This is consistent with the observations at Syowa Station.

    DOI: 10.1029/98JA01187

    DOI: 10.1029/98ja01187

    Web of Science

  174. Application of discovery science to solar-terrestrial physics 査読有り

    T Araki, T Iyemori, M Nose, T Wada, Y Futaana, G Ueno, T Kamei, A Saito

    DISCOVERY SCIENCE   1532 巻   頁: 451 - 452   1998年

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    記述言語:英語   掲載種別:研究論文(学術雑誌)   出版者・発行元:SPRINGER-VERLAG BERLIN  

    Tohru Araki, Toshihiko Iyemori, Masahito Nose, Takaaki Wada, Yoshifumi Futaana, Genta Ueno, Toyohisa Kamei, Akiniro Saito, 1998, &#039;Application of Discovery Science to Solar-Terrestrial Physics&#039;, &lt;i&gt;Discovey Science&lt;/i&gt;, pp. 451-452

    DOI: 10.1007/3-540-49292-5_66

    Web of Science

  175. Automated detection of Pi 2 pulsations using wavelet analysis: 1. Method and an application for substorm monitoring 査読有り

    M Nose, T Iyemori, M Takeda, T Kamei, DK Milling, D Orr, HJ Singer, EW Worthington, N Sumitomo

    EARTH PLANETS AND SPACE   50 巻 ( 9 ) 頁: 773 - 783   1998年

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    記述言語:英語   掲載種別:研究論文(学術雑誌)   出版者・発行元:TERRA SCIENTIFIC PUBL CO  

    Wavelet analysis is suitable for investigating waves, such as Pi 2 pulsations, which are limited in both time and frequency. We have developed an algorithm to detect Pi 2 pulsations by wavelet analysis. We tested the algorithm and found that the results of Pi 2 detection are consistent with those obtained by visual inspection. The algorithm is applied in a project which aims at the nowcasting of substorm onsets. In this project we use real-rime geomagnetic field data. with a sampling rate of 1 second, obtained at mid- and low-latitude stations (Mineyama in Japan, the York SAMNET station in the U.K., and Boulder in the U.S.). These stations are each separated by about 120 degrees in longitude, so at least one station is on the nightside at all times. We plan to analyze the real-time data at each station using the Pi 2 detection algorithm, and to exchange the detection results among these stations via the Internet. Therefore we can obtain information about substorm onsets in real-time, even if we are on the dayside. We have constructed a system to detect Pi 2 pulsations automatically at Mineyama observatory. The detection results for the period of February to August 1996 showed that the rate of successful detection of Pi 2 pulsations was 83.4% for the nightside (18-06MLT) and 26.5% for the dayside (06-18MLT). The detection results near local midnight (20-02MLT) give the rate of successful detection of 93.2%.

    DOI: 10.1186/BF03352169

    Web of Science

    J-GLOBAL

  176. Storm-time magnetic field variations observed by the ETS-VI satellite 査読有り

    N Terada, T Iyemori, M Nose, T Nagai, H Matsumoto, T Goka

    EARTH PLANETS AND SPACE   50 巻 ( 10 ) 頁: 853 - 864   1998年

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    記述言語:英語   掲載種別:研究論文(学術雑誌)   出版者・発行元:TERRA SCIENTIFIC PUBL CO  

    To study the ring current structure in the inner magnetosphere, we have statistically examined the magnetic field data acquired by ETS-VI (the Engineering Test Satellite-VI). During a magnetic storm, the Dst index shows a rapid recovery of its amplitude for about 9 hours on average after the main phase and a subsequent long-lasting slow recovery. We have investigated this "two-step recovery" of the Dst index by obtaining magnetic field vectors and calculating the current structure in the inner magnetosphere for each magnetic storm phase determined by the Dst index. From this study, following results are obtained: (1) Throughout the storm-time, disturbed magnetic fields exhibit clear day-night asymmetry with strong peak in the nightside. (2) During the main phase, southward perturbed field components have a relative bump in the nightside region between similar to 2000 and similar to 0400 MLT and between similar to 4.0 and 6.4 R-E (geocentric distances in Earth radii). (3) The initial rapid recovery of the Dst index is considerably influenced by the nightside currents flowing between similar to 1800 and similar to 0600 MLT and between 5.6 and 7.2 R-E. These currents are thought to be mainly composed of the particles that escape the magnetosphere on the duskside flank, which are simulated in particle tracing in a realistic magnetosphere.

    DOI: 10.1186/BF03352179

    Web of Science

    J-GLOBAL

  177. ULF pulsations observed by the ETS-VI satellite: Substorm associated azimuthal Pc 4 pulsations on the nightside 査読有り

    M Nose, T Iyemori, S Nakabe, T Nagai, H Matsumoto, T Goka

    EARTH PLANETS AND SPACE   50 巻 ( 1 ) 頁: 63 - 80   1998年

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    記述言語:英語   掲載種別:研究論文(学術雑誌)   出版者・発行元:TERRA SCIENTIFIC PUBL CO  

    The magnetic field data from the Engineering Test Satellite-VI (ETS-VI) have been analyzed to investigate the occurrence distributions of pulsations in Pc 3-5 frequency ranges in the magnetosphere. The observation of ETS-VI covered the invariant latitude (ILAT) range of 64.5 degrees-69 degrees ILAT near the geomagnetic equator (-10 degrees-20 degrees magnetic latitude) at all magnetic local time (MLT). Magnetic pulsations were selected by the Fast Fourier Transform method and checked by visual scanning if they have continuous waveforms. From the occurrence distributions of pulsations, we have found distinctive features in the following pulsations: (1) azimuthal Pc 5 pulsation; (2) azimuthal Pc 3 pulsation; (3) radial Pc 4 pulsation on the dayside; (4) azimuthal Pc 4 pulsations on the nightside, In respect of the first three types of pulsations (i.e., the azimuthal Pc 5 pulsation, the azimuthal Pc 3 pulsation, and the radial Pc 4 pulsation on the dayside), the results presented in this study confirm the previous results obtained by other satellite observations. The azimuthal Pc 4 pulsations on the nightside were observed in continuous waveforms lasting for about 10 minutes. Although the azimuthal Pc 4 pulsations on the nightside start at almost the same time as substorm onsets, they are different from Pi 2 pulsations in the magnetosphere. They are observed frequently in the MLT range of 23-04MLT with an occurrence peak at 01-02MLT. We suggest that the azimuthal Pc 4 pulsations on the nightside are excited through coupling to the fast mode Alfven waves which were launched at substorm onset.

    DOI: 10.1186/BF03352087

    Web of Science

    J-GLOBAL

  178. Traveling compression region observed in the mid-tail lobes near substorm expansion phase onset 査読有り

    S. Taguchi, J.A. Slavin, R.P. Lepping, M. Nosé

    European Space Agency, (Special Publication) ESA SP   ( 389 ) 頁: 603 - 607   1996年

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    記述言語:英語   掲載種別:研究論文(学術雑誌)  

  179. A STRONG DAWN DUSK ASYMMETRY IN PC5 PULSATION OCCURRENCE OBSERVED BY THE DE-1 SATELLITE 査読有り

    M NOSE, T IYEMORI, M SUGIURA, JA SLAVIN

    GEOPHYSICAL RESEARCH LETTERS   22 巻 ( 15 ) 頁: 2053 - 2056   1995年8月

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    記述言語:英語   掲載種別:研究論文(学術雑誌)   出版者・発行元:AMER GEOPHYSICAL UNION  

    Using the magnetic field data obtained by the DE-1 polar orbiting satellite, statistical characteristics of transverse Pc5 pulsations in the inner magnetosphere are examined. The occurrence distribution is found to have a strong dawn/dusk asymmetry. The occurrence is most frequent in the region around 72 degrees invariant latitude (ILAT) between 0800 and 1000MLT. The distribution shifts to lower ILAT both in the early morning and in the afternoon sectors. Our results are generally consistent with the occurrence distributions obtained by previous studies except for appreciable differences in the local time of the peak occurrence. The dependence of the transverse Pc5 occurrence on solar wind velocity is also investigated. Results show that the higher the solar wind velocity, the more frequent the Pc5 occurrence. This fact suggests that the energy source of these Pc5's is in the Kelvin-Helmholtz instability (KHI) on the magnetopause. To explain the strong dawn/dusk asymmetry, the dependence of the Pc5 occurrence on the angle between the solar wind velocity and the IMP in the ecliptic plane is investigated. It is found that this angle controls the magnetic local time of Pc5 appearance when the solar wind velocity is small. This dependence may be explained by the low threshold of KHI due to an influence of a quasi-parallel bow shock.

    DOI: 10.1029/95GL01794

    DOI: 10.1029/95gl01794

    Web of Science

▼全件表示

書籍等出版物 2

  1. 地磁気観測で探る宇宙空間環境変動

    能勢正仁( 担当: 分担執筆)

    日本磁気学会報「まぐね」  2020年9月 

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    担当ページ:244-254   記述言語:日本語

  2. データ引用を研究活動の新たな常識に:研究データ利活用協議会(RDUF)リサーチデータサイテーション小委員会の活動

    能勢正仁, 池内有為( 担当: 分担執筆)

    国立国会図書館, カレントアウェアネス  2020年9月 

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    担当ページ:2-4  

    DOI: 10.11501/11546850

科研費 28

  1. 地上多点ネットワークに基づく超高層大気変動の緯度間結合の観測的研究

    研究課題/研究課題番号:21H04518  2021年4月 - 2026年3月

    科学研究費助成事業  基盤研究(A)

    塩川 和夫, 西谷 望, 大山 伸一郎, 横山 竜宏, 大塚 雄一, 藤本 晶子, 野澤 悟徳, 吉川 顕正, 能勢 正仁

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    担当区分:研究分担者 

    地球周辺の宇宙空間のプラズマは磁力線に沿って地球の極域に流れ込み、オーロラに代表される極域の超高層大気の擾乱を引き起こし、さらに中緯度から赤道域に広がっていく。本研究では、既存のアジア域の地上観測ネットワークに加えて、北欧からアフリカ赤道域に至る緯度方向に、夜間大気光を撮像する高感度全天カメラによる地上観測ネットワークを新たに構築し、極域から赤道への超高層大気変動の伝搬過程を2つの経度で同時に測定する。これに人工衛星による観測やモデリングを組み合わせ、極域から赤道域への超高層大気・電磁場変動の発生・伝搬メカニズムとその経度・地方時による拡がりや違いを明らかにする。

  2. 衛星多点観測とシミュレーションに基づくジオスペース酸素イオンの輸送と分布の解明

    研究課題/研究課題番号:21H01147  2021年4月 - 2024年3月

    科学研究費助成事業  基盤研究(B)

    能勢 正仁, 松岡 彩子, 熊本 篤志, 淺村 和史, 山本 和弘

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    担当区分:研究代表者 

    配分額:10530000円 ( 直接経費:8100000円 、 間接経費:2430000円 )

    地球周辺の宇宙空間(ジオスペース)は真空ではなく、プラズマ(正の電荷を帯びた粒子であるイオンと負の電荷を帯びた粒子である電子の混合物)に満ちている。ジオスペースにおけるプラズマは、時として、酸素イオンの密度が急激に増加し、イオン組成が大きく変わることがある。プラズマのイオン組成は、その場所で生起する数多くの電磁気現象の性質を支配するパラメターであるため、その変化原因や変化領域を明らかにすることが極めて重要である。そこで、この研究では、「低エネルギー酸素イオンが、どのように電離層からジオスペースへ輸送され、どのように分布しているのか」について明らかにすることを目的とする。

  3. 多様な学術研究活動を育むアカデミックデータ・イノベーション成熟度モデルの開発

    研究課題/研究課題番号:20H00099  2020年4月 - 2023年3月

    科学研究費助成事業  基盤研究(A)

    梶田 将司, 古川 雅子, 家森 俊彦, 宮野 公樹, 原 正一郎, 元木 環, 小野 英理, 永益 英敏, 松井 啓之, 能勢 正仁, 青木 学聡, 渥美 紀寿

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    担当区分:研究分担者 

    大学における研究データの蓄積・共有・公開及び長期保管を通じて,研究者自らが研究データマネジメントスキル (RDMスキル) を高められるとともに,研究データを軸とした研究コミュニティ形成や異分野連携を可能にするアカデミックデータ・イノベーション成熟度モデルを開発する.本モデルは,研究者が日常的に行う基本RDMスキル,分野ごとに特有のRDMスキル,分野横断型のイノベーションを創発するRDMスキルの3スキル及びこれらのスキル開発方法論により構成される.本研究では,多様な分野の研究者が集う京都大学を実証フィールドとして開発することにより,イノベーションの可能性に満ちた土壌を我が国の学術研究現場に育む.

  4. プラズマ圏極端収縮時の放射線帯消失の撮像

    研究課題/研究課題番号:19H01958  2019年4月 - 2024年3月

    科学研究費助成事業  基盤研究(B)

    尾花 由紀, 坂口 歌織, 細川 敬祐, 能勢 正仁

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    担当区分:研究分担者 

    本研究では、ニュージーランドに新しく高感度全天カメラと誘導磁力計を設置し、放射線帯降下粒子による孤立オーロラの発光と、粒子降下を引き起こすイオンサイクロトロン(EMIC)波動を同時観測することで、以下の科学目標の達成を目指す。
    (1) 地球にごく近い深部磁気圏において、EMIC波動に起因する放射線帯消失が生じていることを立証する。
    (2) 地磁気嵐に伴うプラズマ圏の収縮と放射線帯消失の因果関係を解明する。
    (3) 放射線帯粒子降下による中緯度超高層大気組成への影響評価を行う。
    本研究は、ニュージーランドのミドルマーチ観測点(磁気緯度: -53度, L値: 2.8(磁力線の到達距離が地球半径の 2.8倍の位置))に新しく 高感度全天カメラと誘導磁力計を設置し、放射線帯降下粒子による孤立オーロラの発光と、粒子降下を引き起こすイオンサイクロトロン波動を同時観測することで、以下の科学目標の達成を目指すものである。
    (1) 地球にごく近い深部磁気圏において、イオンサイクロトロン波動に起因する放射線帯消失が生じて いることを立証する。
    (2) 地磁気嵐に伴うプラズマ圏の収縮と放射線帯消失の因果関係を解明する。
    (3) 放射線帯粒子降下による中緯度超高層大気組成への影響評価を行う。
    初年度である2019年度は、過去の観測例を洗い出し、中緯度帯(L < 3)(地球半径の 3 倍以下の位置)のニュージーランドにおけるイオンサイクロトロン波動の周波数と振幅の予想を立て、高感度誘導磁力計に求められるスペックを決定して、購入するインダクションコイルの選別を慎重に行った。その結果、Metronix社製ADU-08eおよびインダクションコイルMFS-06e 2本を購入し、南北・東西方向に設置するのが最低であるとの結論を得た。これらの機器を購入後、高感度誘導磁力計と孤立オーロラ観測用の高感度カメラの観測システムを開発し、高感度誘導磁力計システムについては、名古屋大学稲生地殻変動観測所にて動作確認を行った。さらに大阪電気通信大学内にて、長期動作中の消費電力量のテスト等を行い、太陽電池給電システムの仕様を決定し、必要な太陽電池パネルの発電量や蓄電装置の電気容量等を算出し、在ニュージーランドの現地協力者に必要物品の手配を依頼した。これらの準備が整ったのち、ニュージーランドに出張し、ミドルマーチ観測点にて設置作業を行なった。
    当初の予定では、1年目はスペックの決定後、誘導磁力計を購入し、観測システムを開発し、現地での設置場所の下見を行う予定であった。さらに2年目に誘導磁力計を仮設置し、3年目に本格的な定常観測を開始する計画であった。しかしながら、観測システムの開発が予定以上にスムーズに進行し、電源供給システムについても既存の技術が適合したため開発スケジュールを前倒しすることができた。また現地においても、地主との交渉がスムーズに行え、すぐに掘削する許可を得ることができた上、良好な観測場所も見つけることができた。そのために、予定を繰り上げて2020年3月の現地訪問時に本設置を行うこととし、現地作業を無事済ませることができた。
    これにより、2年目以降はデータ解析に注力することができる体制となった。
    本研究計画の鍵となる誘導磁力計とオーロラ高感度カメラを2020年3月にミドルマーチ観測店に設置したが、その後新型コロナウイルスの流行により、ニュージーランドでは市民の外出規制が行われており、最初の観測データがいまだ回収できていない状況にある。外出規制が解かれたのち速やかに現地協力者にデータの回収と日本への送付を行ってもらう予定である。
    データが入手でき次第、EMIC波動の解析に着手する。特に「あらせ」衛星との共役観測データについては優先的に解析を行う予定である。またプロトタイプ の数値計算モデルを使って EMIC 波動と共鳴することができる荷電粒子のエネルギー (共鳴エネルギー)を導出し、この情報を入力として、オーロラ発光の強度とスペクト ルを計算する。
    さらにこれらの理論的推定値に基づき、観測装置のセッティングを調整するための現地作業を行う予定である。

  5. 磁気インピーダンスセンサーによる地磁気観測実験と稠密観測網展開可能性の探索

    研究課題/研究課題番号:17K18804  2017年6月 - 2021年3月

    科学研究費助成事業  挑戦的研究(萌芽)

    能勢 正仁, 松本 晴久, 小山 幸伸, 北村 健太郎, 松岡 彩子

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    担当区分:研究代表者 

    配分額:6370000円 ( 直接経費:4900000円 、 間接経費:1470000円 )

    微小な地磁気変動を計測するために一般的に用いられている「フラックスゲート磁力計」は一台数百万円と高価である。そこで、「磁気インピーダンス素子」を用いたマイクロ磁気センサーを使って、廉価な地磁気計測システムを独自に開発した。既製品のセンサーを地磁気計測に適したものとなるような改良を加え、センサー治具、AD変換器、Raspberry Piを使ったデータロガーなどを自作し、約40万円で観測システムのプロトタイプを完成させた。そのシステムを用いて、フィールドテスト計測を行い、Sq変動や地磁気脈動、磁気嵐など、自然の地磁気変動現象が問題なく観測できることを確認した。
    数秒から数日の時間スケールで生じる地球の磁場変動は、オーロラの発生時刻やその位置、地球近傍の宇宙空間におけるプラズマの状態などと密接に関わっており、地上の多点で計測を行えば、宇宙天気の概況・全体像を把握することができる。しかし、「フラックスゲート磁力計」は一台数百万円と高価であり、多数用意することは困難である。そこで、今回の研究では、「磁気インピーダンス素子」を用いて、約40万円で地磁気計測システムを独自に開発し、地磁気変動を正確に捉えられることを確認した。廉価であるため、将来的には複数システムを製作して稠密な磁力計ネットワークを展開し、宇宙天気の正確な現状把握や予報に役立てることができる。

  6. 磁気リップル現象の生成機構解明と短周期大気波動の全球的モニタリングへの応用

    研究課題/研究課題番号:17K05669  2017年4月 - 2021年3月

    科学研究費助成事業  基盤研究(C)

    家森 俊彦, 齊藤 昭則, 能勢 正仁

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    担当区分:研究分担者 

    低高度磁場観測衛星でほぼ常時観測される振幅数nT以下の微小な磁場の揺らぎ(磁気リップル)の成因と、当研究で新たに見いだした低緯度昼間側電離圏F層に頻繁に出現する電子密度の波状構造(振幅数%以下、波長100km-300km程度)の成因、およびそれらの間の関連を、ESAが2013年に打ち上げた3機のSwarm衛星により得られた磁場および電子密度データと、タイ・ピマーイでの微気圧変動、GPS-TECおよび降雨量等の地上観測データを用いて調べた。個別のイベント解析および、JAXS/GSMaPを用いた全球的な降雨分布との比較からは、降雨との関連を強く示唆する結果を得たが、明確な結論には至らなかった。
    低高度極軌道衛星で常時観測される磁気リップルは下層大気から電離圏に伝搬する大気波動が原因であると推測されるが、対応する気象現象や波動のモードについては明確な結論が得られていない。また、当研究により低緯度昼間側の電離圏F層に、軌道に沿うスケールが約100km-300kmの波状構造が頻繁に出現することが明らかになった。これら現象は、振幅および空間スケールが小さいが、下層大気で生成された音波モードの大気波動が駆動している可能性が高く、内部重力波に比較して研究が比較的少なかった音波モードの大気波動が電離圏プラズマに及ぼす影響、より一般的には中性大気波動と部分電離気体との相互作用という観点で意義がある。

  7. 地上多点ネットワーク観測による内部磁気圏の粒子・波動の変動メカニズムの研究

    研究課題/研究課題番号:16H06286  2016年4月 - 2021年3月

    科学研究費助成事業  特別推進研究

    塩川 和夫, 西谷 望, 関 華奈子, 大山 伸一郎, 大塚 雄一, 田中 良昌, 尾崎 光紀, 能勢 正仁, 片岡 龍峰, 三好 由純

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    担当区分:研究分担者 

    ・本事業で各観測点に設置されたVLFアンテナ、誘導磁力計、高感度全天カメラ、リオメータ、EMCCDカメラや、平成28年12月に打ち上げられたあらせ衛星、本事業で開発されているモデリングなどを通じ、令和元年度には38件の査読付き論文を国際学術誌に出版した。代表的な成果は以下が挙げられる。
    ・ロシアのZhigansk観測点や米国のRBSP衛星における観測、モデル計算を組み合わせて、電磁イオンサイクロトロン波動(EMIC波動)が数百keVという従来考えられているよりも低いエネルギー範囲の放射線帯電子の消失に貢献していることを明らかにした。また、アラスカのGakona観測点のEMCCDカメラで高速撮像された脈動オーロラと、あらせ衛星で観測された磁気圏ELF/VLF波動(コーラス波動)の明滅の1対1対応を見出し、秒以下の時間スケールのオーロラの脈動が、コーラス波動の微細構造によって作られていることを世界で初めて明らかにした。さらにフィンランドのKannuslehto観測点とあらせ衛星で同時観測された磁気圏ELF/VLF波動を詳細に解析し、磁気圏赤道面における地球磁場の曲率が、ここで生成される波動の特性を大きく左右していることを明らかにした。これらの電磁波動の衛星ー地上観測の成果は、人類の宇宙利用の脅威となる放射線帯粒子の生成・消失の機構の解明につながる重要な成果である。
    ・ノルウェーのトロムソ観測点で得られた熱圏風のデータ解析から、オーロラサブストーム開始前後の熱圏風の変動や地磁気静穏時の熱圏風の動態を明らかにした。また、北欧と南極昭和基地の大型レーダーとあらせ衛星の同時観測により、高エネルギー粒子の降込みに伴う中間圏レーダーエコーの発生を見出した。これらの観測は、宇宙空間からの高エネルギープラズマ粒子の流入に対する地球大気の応答を明らかにする上で重要な成果である。
    ・フィンランド、アイスランド、カナダ、ロシア、アラスカ、日本などの既存の観測点の自動定常観測を維持・継続している。残っているカナダのNain観測点もすべての装置及び記録計の設置を終了し、キャンペーンベースで稼働させることができており、得られたデータの解析も進められている。
    ・引き続き、これらの観測で得られるデータをERGサイエンスセンターとIUGONETによるデータベースを利用してデータベース化して公開し、国内・海外との共同研究を促進することができている。
    ・定常観測を継続している日本のERG(あらせ)衛星の軌道に合わせて、令和元年度の秋にもキャンペーン観測を行った。また、米国のVan Allen Probe衛星・THEMIS衛星などの内部磁気圏衛星との同時観測データの解析を進めることもできている。
    ・波動と粒子の相互作用を局所的およびグローバルに評価するモデリングの開発を継続し、これらの観測と比較することで、モデルの改良と粒子加速・消失の定量評価を行いつつある。
    ・これらの地上・衛星観測、モデリングから、数多くの研究成果が得られている。
    ・カナダのNain観測点は、電源が得られない場合は発電機を活用してあらせ上空通過時などに観測を行ってデータを取得していく。
    ・本研究では8か所の観測点・5種類の機器から大量のデータを得ている。これらの観測データはすべて大容量ストレージに保管され、世界的に広く使われているCDFフォーマットに変換されて、ネットワークを介して世界の研究者に公開されている。昨年度に引き続き、新しく得られてくるデータも世界の研究者に公開し、データ利用の促進と成果の創出をはかっていく。
    ・本事業ではホームページ(http://www.isee.nagoya-u.ac.jp/dimr/PWING/)を立ち上げてデータの説明や進捗状況、データへのリンク先などを公開している。このホームページを引き続き運用し、情報発信をはかっていく。さらに、関連研究の国際ワークショップや国際シンポジウムを開催して、成果の創出をはかっていく。
    ・本研究の成果は、科学論文として発表していくだけでなく、さまざまな形で社会へ発信していくことが重要である。このために、出前授業や、大学院生・若手研究者向けの国際スクール、重要な成果のプレスリリースなどを実施していく。

  8. 衛星多点観測と計算機シミュレーションによる内部磁気圏のイオン組成変化要因の探究

    研究課題/研究課題番号:16H04057  2016年4月 - 2019年3月

    科学研究費助成事業 

    能勢 正仁

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    担当区分:研究代表者 

    配分額:14560000円 ( 直接経費:11200000円 、 間接経費:3360000円 )

    日本が2016年12月にうちあげた「あらせ衛星」の観測データの解析および計算機シミュレーションにより、酸素イオントーラスおよびイオンと長周期地磁気脈動のドリフトバウンス共鳴現象に関する研究を行った。酸素イオントーラスに関しては、その形状が軸対象ではなく朝側に偏った三日月形であることが、世界で初めて明らかにされた。ドリフトバウンス共鳴がリングカレントのエネルギー増加に少なからぬ影響を及ぼしていることやそれにはイオン種依存性があること、イオンフラックスの空間勾配が共鳴の重要なパラメターになり得ること、などの新しい発見が得られた。以上の研究成果を含め、査読付き国際学術誌に25編の論文を出版した。
    日本が打ち上げた国産の「あらせ衛星」が観測したデータに基づく研究成果であるため、日本発の科学成果を世界に向けて発信することができた。酸素イオントーラスの経度方向の構造が軸対象ではなく朝側に偏っていること、およびドリフトバウンス共鳴がリングカレントの発達に効果的であることやそのイオン種依存性などは、これまでに報告のなされたことのないもので、学術的に大きな意義のある発見である。人類が宇宙空間を利用していくに当たって宇宙天気予報の研究が進んでおり、その実用化のために理解すべき、宇宙空間におけるイオンのダイナミクスの一端を明らかにした点で社会的な意義があると考えている。

  9. 深内部磁気圏における高エネルギーイオン生成・輸送機構とそのイオン種依存性の解明

    研究課題/研究課題番号:25287127  2013年4月 - 2016年3月

    能勢 正仁

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    担当区分:研究代表者 

    配分額:12740000円 ( 直接経費:9800000円 、 間接経費:2940000円 )

    気象衛星ひまわりやGPS衛星が飛翔する地球周辺の宇宙空間(内部磁気圏)は、荷電粒子からなるプラズマで満たされている。内部磁気圏のプラズマは、平時は水素イオンが主成分であるが、磁気嵐が起こると酸素イオンの含有量が急激に増加する。この研究では、内部磁気圏を観測している科学衛星のデータを解析し、その原因の究明を行った。その結果、「電離層から内部磁気圏へ酸素イオンが直接流出しており、それが磁場双極子化に伴う微小磁場擾乱によりその場で選択的に加速される」ためであることが明らかになった。

  10. 地上・衛星の多点観測データを用いた深内部磁気圏擾乱の発達・減衰に関する総合解析

    研究課題/研究課題番号:22740322  2010年 - 2012年

    能勢 正仁

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    担当区分:研究代表者 

    配分額:4160000円 ( 直接経費:3200000円 、 間接経費:960000円 )

    磁気圏擾乱の指標であるDst指数には、リングカレントなどの磁気圏電流と地球内部に誘起された電流の寄与が混在している。これまで、地球内部誘起電流の寄与は約25%で一定と考えられてきたが、今回の研究により、その割合は20%から55%の間で変化し、Dst指数の時間変化率と高い相関を持つことが明らかになった。また、リングカレントの発達に関しては、過去に報告されてきたような「プラズマシートからの高エネルギー粒子の流入」よりも、「その場に既に存在していた低エネルギー粒子が短周期の磁場擾乱によって受けるローカルな非断熱的加速」がより重要な役割を果たしていることが分かった。

  11. 汎地球的地磁気観測によるPi2地磁気脈動リアルタイム検出システムの構築

    研究課題/研究課題番号:17740327  2005年 - 2006年

    能勢 正仁

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    担当区分:研究代表者 

    配分額:3500000円 ( 直接経費:3500000円 )

    2005年7月から9月にかけて、イギリス(ランカスター大学)、ドイツ(フルステンフェルドブルク観測所)・アメリカ(ジョンズホプキンス大学応用物理研究所)・メキシコ(テオロユーカン観測所)、日本(柿岡地磁気観測所、峰山観測所)の合計6観測所を順次訪問し、ウェーブレット解析を使ってPi2地磁気脈動を自動検出するソフトウェアをインストールした。Pi2地磁気脈動が検出されると、その波形や検出時刻などの結果は、電子メールで申請者の所属する京都大学へ送られ、WWWで公開されるようになっている。各観測所では、地磁気データをリアルタイムで収集しているので、検出結果もほぼリアルタイムでWWWから見られるようになっている。WWWアドレスは、http://swdcli40.kugi.kyoto-u.ac.jpである。また、このようなデータ収集で得られた経験を基にして、サブストームの発生を中低緯度の地磁気観測から推定するための新しい地磁気指数を考案し、その算出を行い始めた。この新しい指数をAE指数や静止軌道衛星の粒子フラックスと比較し、それぞれの間に比較的よい相関があることが分かった。その他に、柿岡地磁気観測所とHermanus地磁気観測所のデータを用いて、Pi2地磁気脈動の経度方向の構造を統計的に調べた結果、その経度方向の波数はほぼ0に近い値となり、全球的に同位相で振動が起こっていることが明らかになった。
    以上の研究内容・活動を国内外の学会で5回(国内3回・国外2回)にわたって報告を行った。研究成果は、Nose et al.,Earth Planet.Space,58,775-783,2006とNose et al.,Proceedings of the Eighth International Conference on Substorms(ICS-8),209-214,2006の2つの学術論文として発表した。加えて、関連した研究として主著論文1編、共著論文2編を発表した。

  12. 1920年代にまで遡る高時間分解能地磁気デジタルデータベース

    研究課題/研究課題番号:18HP8018  2018年4月 - 2019年3月

    科学研究費補助金(研究成果公開促進費(データベース) 

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    担当区分:研究代表者  資金種別:競争的資金

    配分額:1700000円

  13. 1920年代にまで遡る高時間分解能地磁気デジタルデータベース

    研究課題/研究課題番号:16HP8026  2016年4月 - 2017年3月

    科学研究費補助金(研究成果公開促進費(データベース) 

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    資金種別:競争的資金

    配分額:1700000円

  14. 1920年代にまで遡る高時間分解能地磁気デジタルデータベース

    研究課題/研究課題番号:15HP8028  2015年4月 - 2016年3月

    科学研究費補助金(研究成果公開促進費(データベース) 

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    担当区分:研究代表者  資金種別:競争的資金

    配分額:1600000円

  15. 深内部磁気圏における高エネルギーイオン生成・輸送機構とそのイオン種依存性の解明(国際共同研究強化)

    研究課題/研究課題番号:15KK0161  2015年

    国際共同研究加速基金(国際共同研究強化)

    能勢 正仁

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    担当区分:研究代表者 

    配分額:14300000円 ( 直接経費:11000000円 、 間接経費:3300000円 )

  16. 1920年代にまで遡る高時間分解能地磁気デジタルデータベース

    研究課題/研究課題番号:268023  2014年4月 - 2015年3月

    科学研究費補助金(研究成果公開促進費(データベース) 

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    資金種別:競争的資金

    配分額:2300000円

  17. 下層大気の大規模擾乱に起因する超高層電磁場変動の解明とその応用研究

    研究課題/研究課題番号:25287128  2013年4月 - 2016年3月

    家森 俊彦

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    担当区分:研究分担者 

    低高度精密磁場観測衛星が、中低緯度電離圏でほぼ常時観測する微細な磁場変動(magnetic ripplesと命名)は、これまでその存在すら認識されていなかった微細な沿磁力線電流の空間構造であることを世界で初めて明らかにした。また、それらの振幅の季節・地方時・緯度依存性や変動の時間スケールなどを求めた。地理的依存性や地震・火山噴火時に地上で観測される磁場、微気圧およびGPS-TEC変動も考慮することにより、それらが、下層大気の擾乱を起源とし、電離圏まで伝搬した重力音波が、電離層でのダイナモ作用を介して電離層に電流を流し、それが磁力線に沿って発散し沿磁力線電流になっていることを明らかにした。

  18. 1920年代にまで遡る高時間分解能地磁気デジタルデータベース

    研究課題/研究課題番号:248032  2012年4月 - 2013年3月

    科学研究費補助金(研究成果公開促進費(データベース) 

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    資金種別:競争的資金

    配分額:2200000円

  19. サブストームトリガー・駆動機構の完全解明に向けた先端研究

    研究課題/研究課題番号:22340145  2010年 - 2012年

    町田 忍

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    担当区分:研究分担者 

    サブストームは地球磁気圏・電離圏で発生する大規模なエネルギー解放現象であるが、そのトリガー機構と駆動機構の解明を目指して、衛星および地上同時観測で得られた最新データを用いて研究を実施した。その結果、われわれがかねてより提案しているサブストームのトリガー・駆動機構モデルの正当性を確認することができた。また、サブストームに関連したオーロラ電波放射(AKR)について幾つかの重要な知見を得た。

  20. 地球惑星科学仮想データセンターの構築と機能の実証的研究

    研究課題/研究課題番号:20244081  2008年 - 2010年

    家森 俊彦

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    担当区分:研究分担者 

    大小様々な組織が提供する地球惑星科学関係のデータベースを、メタデータのデータベースを核として、サイバースペースで結合し、異分野横断・学際研究推進の母体となる『地球惑星科学仮想データセンター』創出の実現可能性を実証的に研究した。実施にあたっては、大学間連携プロジェクト『超高層大気長期変動の全球地上ネットワーク観測・研究』(IUGONET)と密接に協力し、使用するメタ情報フォーマットを検討、SPASE data modelが最適であると判断した。IUGONETと協力してシステムを開発し、微気圧観測データと地磁気データを具体例として、メタデータの入力およびデータベースの構築を実施した。

  21. 下層大気の大規模擾乱に起因する宇宙空間電磁気現象の研究

    研究課題/研究課題番号:19654073  2007年 - 2008年

    萌芽研究

    家森 俊彦

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    担当区分:研究分担者 

    当研究は、地震や火山噴火、台風など地球表面付近の現象が、それより上層の海洋、大気の運動を通して、電離圏や磁気圏に電磁気学的現象を発生させるメカニズムの理論的考察と、観測および数値シミュレーションによる検証を全体構想とする。本年度は、下記の成果が得られた。
    1. 平成18年夏から観測を開始した微気圧観測データと、近接地点の地磁気観測データを統計的に解析することにより、理論的に予想されてきた3つの周波数帯に、気圧、磁場ともスペクトル密度ピークが存在することを、データを増やすことにより、統計的により確実にすることができた。また、微気圧振動のピークは秋に明瞭に見られるという前年度示唆された結果をより確実なものにした。
    2. 平成20年度は微気圧観測システムをペルーのアンコン観測所に設置した。このデータは、磁場観測データと共に昨年末から京都大学に転送されており、解析を進めつつある。
    3. 2004年12月のスマトラ地震時に、中国南部で観測された約20秒余りの周期の地磁気脈動が、その場所での磁力線共鳴周期とほぼ一致すること、また、それ以外の場所では見られないことを、それぞれ、理論的計算およびデータ解析から確認した。このことは、この約20秒余りの周期の地磁気脈動が、スマトラ地震によって引き起こされた磁力線共鳴現象であることを強く示唆し、下層大気の大規模擾乱に起因する宇宙空間電磁気現象の一つであることを示す。
    4. 研究協力者と共に、数値シミュレーションで確認するための計算コードの3次元化に着手した。

  22. 複数衛星観測による深内部磁気圏の磁場構造変化とイオン組成変化に関する研究

    研究課題/研究課題番号:19740303  2007年 - 2008年

    能勢 正仁

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    担当区分:研究代表者 

    配分額:3520000円 ( 直接経費:3100000円 、 間接経費:420000円 )

    これまでは、静止衛星軌道より内側のリングカレント領域(高度20000-30000km付近)の磁場構造はそれほど大きく変化しないと考えられることが多く、双極子磁場による近似が行われてきた。しかしながら、MDS-1衛星の磁場観測により、このような領域でもサブストームに伴う磁場双極子化や高周波の磁場擾乱が現れたり、磁場構造が強く引き伸ばされた形状になったりするように、内部磁気圏の磁場構造は想像以上に変動していることが明らかになった。こうした磁場変動は、特に酸素イオンを選択的に加速し、リングカレントのイオン組成変化に重要な役割を果たしていることが分かった。

  23. リモートセンシングによる磁気圏・極域電離圏プラズマの動態の解明

    研究課題/研究課題番号:18540443  2006年 - 2008年

    田口 聡

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    担当区分:研究分担者 

    地球の周辺の宇宙空間には電気を帯びた微粒子が存在しており, 様々な場所でそれぞれ固有の速さで動いている. 本研究では, その微粒子の一部が姿を変えた中性の粒子の運動を検出する撮像のデータを主に用いて, 電気を帯びた微粒子であるイオンの太陽風から磁気圏への直接的な流入, 地球磁気圏の外壁であるマグネトポーズの運動, 電離圏から磁気圏へと上昇するイオンの流れに関して, これまでに知られていない性質を見出した.

  24. ユーラシア大陸横断磁力計列構築と精密衛星磁場観測に基づく自然電磁環境変動の研究

    研究課題/研究課題番号:17403008  2005年 - 2007年

    家森 俊彦

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    担当区分:研究分担者 

    地磁気は超高層物理学および地球内部電磁気学的研究にとって最も基礎的で重要な物理量であり、汎世界的に分布する観測所で長期間安定した測定をする必要がある。当研究では、地磁気ディジタルデータの巨大な空白地帯となっているシルクロード沿いおよびその延長線上の地域に存在する約12ヶ所の地磁気観測所のうち3ヶ所に、高精度ディジタル磁力計を設置し、中緯度のユーラシア大陸を横断する長大な磁力計ネットワークを構築することを計画し実施した。そして、上記ネットワークで取得されたデータとOersted精密磁場観測衛星等のデータを用いて、地磁気脈動の東西伝搬、オーロラ帯に流れ込む沿磁力線電流の刻々の時間変化の推定、電離層ダイナモ電流の逐日および経度依存変動やその原因となる下部電離層の中性風の推定、磁気圏サブストーム開始の指標となるPi2型地磁気脈動のリアルタイム検出等、このネットワークの特徴を生かした超高層物理学的研究を推進した。また、トルコ、中央アジアなど、地殻活動の活発なシルクロード沿いの地球内部電磁気学的諸観測にとって基準となる高精度・高時間分解能地磁気データを提供することも、目的の一つとした。Pi2型地磁気脈動のリアルタイム検出結果は京都大学大学院理学研究科地磁気世界資料解析センターのホームページから公開した。(URL:http://swdcli40.kugi.kyoto-u.ac.jp/pi2/)また、トルコおよびインドからの観測データ(毎分値および毎秒値)は、電話回線およびインターネットを経由して、準リアルタイムで京都に送られている。

  25. マグネトグラム古記録の数値化技術の開発とそれを用いた太陽風長期変動の研究

    研究課題/研究課題番号:16654076  2004年 - 2005年

    萌芽研究

    家森 俊彦

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    担当区分:研究分担者 

    (1)古いマグネトグラム記録をディジタル画像ファイル化する作業およびその画像を処理してデータベース化する手順の効率化を進めた。
    (2)データベース化した処理済みの画像ファイルをwebから公開した。(http://swdcft49.kugi.kyoto-u.ac.jp/film/index-j.html)
    (3)磁気圏境界面での速度シアーによるケルビンヘルムホルツ型不安定性が主要な発生メカニズムであるため、太陽風速度と関係があるPc5型地磁気脈動の性質を用いて、太陽風観測データのない1960年以前の地磁気観測データから太陽風速度を推定することを目的の一つにした。そのために、まず、太陽風速度とPc5型地磁気脈動の振幅の関係を調べた。その結果、600km/s以上の高速太陽風の場合も、太陽風速度と脈動の振幅の間の正相関の関係は、600km/s以下の場合の延長上にあることがわかった。また、Pc5型地磁気脈動の発生には、太陽風密度の変動が影響していることを示唆する結果が得られた。
    (4)2次元画像処理手法を用いて連続なグラフ部分のみを取り出す試みを行った。
    (5)2005年11月に英国エディンバラで開催されたディジタルデータ保存に関する国際会議PV2005に家森が出席し、当研究の成果の一部を発表した。
    (6)ディジタル画像化されたデータを用いて、1960年のチリ大地震の時の世界各地の地磁気変化を調べた。その結果、震源から遠く離れたヨーロッパやアフリカでも地震波による磁力計の振動の影響が出ていること、また、イースター島では、津波の通過したと考えられる時刻に、津波による海洋ダイナモ電流が原因と考えられる地磁気変化が観測されていたことがわかった。この結果は、2006年5月の日本地球惑星科学連合2006年大会で発表を予定している。

  26. 人工衛星塔載型磁力計方式での地上観測所3成分絶対磁場測定装置の試験研究

    研究課題/研究課題番号:16540406  2004年 - 2005年

    亀井 豊永

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    担当区分:研究分担者 

    平成17年度は非常に残念ながら研究代表者の病状悪化のため年度の延期を打診したが、だめだった。このため、1つの試作機を完成するのではなく、いろいろな部分性能評価を重視することとした。平成16年度で作成した、非磁性セオドライトの回転部分は磁場測定は1分1回転で予定通り1/30秒毎のAD測定に耐える、また、星座からの角度確定では、広角で角度1度以内から10分程度でに決められるがその磁場測定とのタイミングあわせは非常に難しい。望遠鏡を使用した侠角1分精度で星座を探すためには非常に高速のCPUが必要となり回転が安定しないと仮定した地上装置とノートPCではやはり無理がある。そのため、2つの予定外の方法を試すことにした。1つは値下がりした民生用ハイビジョンカメラと非常に高速のCPUと2GB高速大メモリーを備えたデスクトップPCを試した、しかしこれは非圧縮DVカメラ(3色約15MHz固定)と違い画像が25MHzMPEG圧縮のため画像が非常に荒く、しかも時間遅れが不安定で0,3-0.7秒遅れでPCに送り込まれるためHDV信号や圧縮デジタル機能を使用するのはこの角度測定用途にむかず、単純にHDVのアナログD3信号を直接ベースバンド(3色約150MHz)で映像取り込みして処理する必要がある。もう1つの方法は、余り早く回転させるとどのような狭角測定法でも無理がでるので、回転軸方向に侠角は星座判定をする方法にすることである。このためには望遠鏡方向に邪魔がないようにセオドライトの幾何学的配置を見直しセオドライトの支柱が望遠鏡とカメラを避けるように設計を工失する。なお、十分テストは出来ていないが、回転上の複数の星が明らかになった状態で複数の視野に連続に入ってくる明るい星や昼間の太陽タイミングを狙う場合にはやはり圧縮HDV信号は無理でD3信号を基準にHDVのベースバンドの信号を使用して角度の秒単位での角度測定は実用になると考える。このほかの、セオドライトの180度自動回転や気象条件や耐久性を試すテストは更に後ほど行うことになる。

  27. 非対称磁気圏構造形成の物理とモデル化

    研究課題/研究課題番号:13640451  2001年 - 2002年

    家森 俊彦

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    担当区分:研究分担者 

    (1)エールステッド衛星による最新の観測データを、ネットワークを用いてデンマーク気象研究所から転送しワークステーション上にデータベース化した。(2)磁場観測データを解析するためのソフトウェアを作成した。ソフトウェアは、過去の研究過程で作成されたプログラムを改良・移植するほか、新たに内部磁気圏電流モデルとそれによる地上磁場変化を計算するソフトウェアを作成した。(3)これまでに蓄積された人工衛星磁場観測データのうち、DE-1衛星磁場観測データを解析し、磁場・電流構造を定量的に解析した。(4)地上磁場データから沿磁力線電流を推定した。(5)家森と荒木、能勢がH13年8月にハノイで開催されたIAGA-IASPEI合同科学大会に参加し、これまでの研究結果を発表した。
    (6)中低緯度におけるエールステッド衛星磁場観測データから、極域電離層に出入りする"net field-aligned current"の地方時分布を求めた。その結果、正午前に流入し、真夜中前から流出していることが確認された。(7)DE-1衛星磁場観測データ解析からも、昼間側から流入し、夜側から流出する"net field-aligned current"の存在を確認することができた。(8)電離層レベルでの電流構造と物理を今後更に詳細に調べるために、SuperDARN極域HFレーダーデータの整備を行った。(9)平成14年9月にデンマークで開催された第4回エールステッド科学会議に家森が出席し、上記成果を発表した。平成15年4月のEGS-AGU-EUG合同会議にも家森が出席し発表した。

  28. 地球磁気圏のイオン組成に関する研究

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    資金種別:競争的資金

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担当経験のある科目 (本学) 6

  1. 物理学実験

    2020

  2. 宇宙電磁観測セミナー2A-2E

    2020

  3. 卒業研究B

    2020

  4. 卒業研究A

    2020

  5. 宇宙電磁観測セミナー1A-1D

    2020

  6. データ解析処理論

    2020

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担当経験のある科目 (本学以外) 1

  1. 地球物理学特論

    2021年9月 - 2022年3月 大阪電気通信大学)

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    科目区分:大学院教養科目  国名:日本国