Faculty Profiles - SHIOKAWA, Kazuo

Papers - SHIOKAWA, Kazuo

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Three-Dimensional Fourier Analysis of Atmospheric Gravity Waves and Medium-Scale Traveling Ionospheric Disturbances Observed in Airglow Images in Hawaii Over Three Years Reviewed

Hideto Naito, Kazuo Shiokawa, Yuichi Otsuka, Hatsuki Fujinami, Takuma Tsuboi, Takeshi Sakanoi, Akinori Saito, Takuji Nakamura

Journal of Geophysical Research: Space Physics Vol. 127 ( 10 ) 2022.10

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

Three-dimensional Fourier spectral analysis of airglow images is a useful technique to provide propagation characteristics of atmospheric gravity waves (AGWs) in the mesopause region and medium-scale traveling ionospheric disturbances (MSTIDs) in the thermosphere observed at emission wavelengths of 557.7 nm (altitudes: 90–100 km for AGWs) and 630.0 nm (200–300 km for MSTIDs). However, a statistical study of spectral analysis of airglow images over years has not been done yet at Hawaii. Here, we report the first spectral analysis of AGWs and MSTIDs using airglow images obtained at Haleakala (20.71°N, 203.74°E), Hawaii, during the three years from 2013 to 2016. The power spectral density (PSD) of AGWs tends to be larger toward north to northeast in summer and from north to west and southward in winter. The eastward (summer) and westward (winter) preferences are consistent with a wind-filtering mechanism of AGWs by a mesospheric jet. Some correspondence is found between the locations of tropospheric convection activities and AGW propagation directions, suggesting that these mesospheric AGWs are originated from the troposphere. The PSDs of MSTIDs are larger in solstice than in equinox. This PSD enhancement in solstice is consistent with a sporadic-E (Es) layer occurrence in either northern or southern hemisphere, suggesting that the MSTIDs over Hawaii could be caused by a coupling process between the Perkins and Es layer instabilities. A small correlation was found between the PSDs of AGWs in the mesopause region and the PSDs of MSTIDs, suggesting that the MSTIDs are partly caused by AGWs from the mesopause region.

DOI： 10.1029/2022JA030346

Web of Science

Scopus

Multi-Event Study of Simultaneous Observations of Isolated Proton Auroras at Subauroral Latitudes Using Ground All-Sky Imagers and the Van Allen Probes Reviewed

Nakamura Kohki, Shiokawa Kazuo, Nose Masahito, Nagatsuma Tsutomu, Sakaguchi Kaori, Spence Harlan, Reeves Geoff, Funsten Herbert O., MacDowall Robert, Smith Charles, Wygant John, Bonnell John, Mann Ian R.

JOURNAL OF GEOPHYSICAL RESEARCH-SPACE PHYSICS Vol. 127 ( 9 ) 2022.9

Language：English Publishing type：Research paper (scientific journal) Publisher：Journal of Geophysical Research: Space Physics

Isolated proton auroras (IPAs) appearing at subauroral latitudes are generated by energetic protons precipitating from the magnetosphere through interaction with electromagnetic ion cyclotron (EMIC) waves. Thus, an IPA is the ionospheric projection of the spatial and temporal variation of wave-particle interaction regions in the magnetosphere. In this study, we conducted unique multi-event analysis of simultaneous observations of IPAs and their source regions on 22 April, 7 September, and 22 March 2018, using all-sky imagers at subauroral latitudes and the Van Allen Probes. When the satellite footprint passed over the IPAs associated with ground Pc1 geomagnetic pulsations, locally generated He+-band EMIC waves with the same frequencies as the ground Pc1 pulsations were observed in all events. The IPAs and EMIC waves had comparable narrow widths in the latitudinal direction. The EMIC waves appeared during the rapid enhancement of the ring current proton flux at energy range of ∼10–50 keV, while they disappeared at the rapid decrease of the electron density. From these results, we conclude that the boundaries of the localized IPAs and EMIC waves were determined by the overlap region of energetic proton enhancement and the plasmasphere. This overlap of ring-current protons and plasmasphere is a favorable condition for the pitch-angle scattering of protons by the EMIC waves. Characteristic magnetic and electric field variations with the IPAs were not observed by the satellite, indicating that the IPAs were not accompanied by field-aligned currents comparable to that of oval auroral arcs.

DOI： 10.1029/2022JA030455

Web of Science

Scopus

Statistical Study of Subauroral Arc Detachment at Athabasca, Canada: New Insights on STEVE Reviewed

Yadav Sneha, Shiokawa Kazuo, Otsuka Yuichi, Connors Martin

JOURNAL OF GEOPHYSICAL RESEARCH-SPACE PHYSICS Vol. 127 ( 9 ) 2022.9

Language：English Publishing type：Research paper (scientific journal) Publisher：Journal of Geophysical Research: Space Physics

We present the first comparative statistical study of subauroral arc detachment from the main auroral oval at Athabasca (magnetic latitude = 61.5°N), Canada, for three different types of subauroral arcs: pure red arc, red arc with simultaneous emission in green-line (red + green arc), and STEVE (strong thermal emission velocity enhancement). Based on 15-years (2006–2020) of all-sky imaging observations, this study not only uncovers the occurrence characteristics of different arcs but also provides important insights into the specific geomagnetic conditions under which STEVE develops. Red arc was the most common subauroral arc (139 events), followed by red + green arc (42 events), and STEVE (26 events) was a rare phenomenon. The detachment rate of red and red + green arcs exhibits dependence on both the solar flux and geomagnetic activity. The detachment rate of STEVE was higher during premidnight, whereas that of red and red + green arcs was higher around the midnight sector. The geomagnetic activity was relatively higher for STEVE, the decrease in the AL index and local X-component magnetic variations being ∼2–3 times higher for STEVE as compared to other arcs. STEVE shows a strong association with asymmetric ring current in terms of prominent bay-like enhancement in ASY-H index prior to its detachment. Such bay-like enhancement was ∼4 times higher for STEVE as compared to other arcs. STEVE events were accompanied by dispersionless injection for both electron and proton flux at geosynchronous orbit. These results unambiguously suggest that STEVE develops after substorm associated energy injection and significant intensification of the asymmetric ring current.

DOI： 10.1029/2021JA029856

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Scopus

Quantifying the Size and Duration of a Microburst‐Producing Chorus Region on 5 December 2017 Reviewed Open Access

S. S. Elliott, A. W. Breneman, C. Colpitts, J. M. Pettit, C. A. Cattell, A. J. Halford, M. Shumko, J. Sample, A. T. Johnson, Y. Miyoshi, Y. Kasahara, C. M. Cully, S. Nakamura, T. Mitani, T. Hori, I. Shinohara, K. Shiokawa, S. Matsuda, M. Connors, M. Ozaki, J. Manninen

Geophysical Research Letters Vol. 49 ( 15 ) page： e2022GL099655 2022.8

A Story of Developing the Idea of Plasma-Sheet Flow Braking Reviewed Open Access

Shiokawa Kazuo

FRONTIERS IN ASTRONOMY AND SPACE SCIENCES Vol. 9 2022.8

Language：English Publishing type：Research paper (scientific journal) Publisher：Frontiers in Astronomy and Space Sciences

This paper reports a story of developing the idea of Earthward ion flow braking in the near-Earth plasma sheet and its relationship with substorm onset processes. This idea and the data that support it are the basis for today’s two competing models for substorms: the near-Earth neutral-line model and the current disruption model. The idea was developed when the author was staying at the Max Planck Institute for Extraterrestrial Physics (MPE) from July 1996 to June 1997. The story addresses the colleagues and mentors who had contributed to the development of this idea. The lessons learned from this story are also summarized for students and early-career scientists for their development of new scientific ideas.

DOI： 10.3389/fspas.2022.957776

Open Access

Web of Science

Scopus

Collaborative Research Activities of the Arase and Van Allen Probes Reviewed Open Access

Y. Miyoshi, I. Shinohara, S. Ukhorskiy, S. G. Claudepierre, T. Mitani, T. Takashima, T. Hori, O. Santolik, I. Kolmasova, S. Matsuda, Y. Kasahara, M. Teramoto, Y. Katoh, M. Hikishima, H. Kojima, S. Kurita, S. Imajo, N. Higashio, S. Kasahara, S. Yokota, K. Asamura, Y. Kazama, S.-Y. Wang, C.-W. Jun, Y. Kasaba, A. Kumamoto, F. Tsuchiya, M. Shoji, S. Nakamura, M. Kitahara, A. Matsuoka, K. Shiokawa, K. Seki, M. Nosé, K. Takahashi, C. Martinez-Calderon, G. Hospodarsky, C. Colpitts, Craig Kletzing, J. Wygant, H. Spence, D. N. Baker, G. D. Reeves, J. B. Blake, L. Lanzerotti

Space Science Reviews Vol. 218 ( 5 ) page： 38 2022.8

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

Abstract

This paper presents the highlights of joint observations of the inner magnetosphere by the Arase spacecraft, the Van Allen Probes spacecraft, and ground-based experiments integrated into spacecraft programs. The concurrent operation of the two missions in 2017–2019 facilitated the separation of the spatial and temporal structures of dynamic phenomena occurring in the inner magnetosphere. Because the orbital inclination angle of Arase is larger than that of Van Allen Probes, Arase collected observations at higher $L$-shells up to $L \sim 10$. After March 2017, similar variations in plasma and waves were detected by Van Allen Probes and Arase. We describe plasma wave observations at longitudinally separated locations in space and geomagnetically-conjugate locations in space and on the ground. The results of instrument intercalibrations between the two missions are also presented. Arase continued its normal operation after the scientific operation of Van Allen Probes completed in October 2019. The combined Van Allen Probes (2012-2019) and Arase (2017-present) observations will cover a full solar cycle. This will be the first comprehensive long-term observation of the inner magnetosphere and radiation belts.

DOI： 10.1007/s11214-022-00885-4

Other Link： https://link.springer.com/article/10.1007/s11214-022-00885-4/fulltext.html

Signatures of Auroral Potential Structure Extending Through the Near‐Equatorial Inner Magnetosphere Reviewed Open Access

S. Imajo, Y. Miyoshi, K. Asamura, I. Shinohara, M. Nosé, K. Shiokawa, Y. Kasahara, Y. Kasaba, A. Matsuoka, S. Kasahara, S. Yokota, K. Keika, T. Hori, M. Shoji, S. Nakamura, M. Teramoto

Geophysical Research Letters Vol. 49 ( 10 ) 2022.5

Slow Contraction of Flash Aurora Induced by an Isolated Chorus Element Ranging From Lower-Band to Upper-Band Frequencies in the Source Region Reviewed Open Access

Mitsunori Ozaki, Satoshi Yagitani, Kazuo Shiokawa, Yoshimasa Tanaka, Yasunobu Ogawa, Keisuke Hosokawa, Yoshiya Kasahara, Yusuke Ebihara, Yoshizumi Miyoshi, Kousuke Imamura, Ryuho Kataoka, Shin-ichiro Oyama, Teppei Chida, Akira Kadokura

GEOPHYSICAL RESEARCH LETTERS Vol. 49 ( 9 ) 2022.5

Language：English Publishing type：Research paper (scientific journal) Publisher：AMER GEOPHYSICAL UNION

Flash aurora driven by an isolated chorus element can be a useful ionospheric indicator for identifying the source wave properties via wave-particle interactions. Using ground observation and modeling approaches, here we report the temporal characteristics of flash aurora that depend on the chorus frequency width and the sweep rate. We found that the contraction time increases more than the expansion time in patchy auroral variations, due to the difference in the minimum electron energies resonated with the chorus wave packet away from the equatorial source to higher latitudes. Especially, the contraction time strongly depends on the higher-frequency chorus waves due to cyclotron resonance with lower-energy electrons. The model calculations support that the chorus element ranges from lower-band to upper-band frequencies with respect to half the gyrofrequency at the exact generation region. Our study provides the prompt (milliseconds) chorus-driven electron dynamics through the spatiotemporal characteristics of flash aurora in the ionosphere.

DOI： 10.1029/2021GL097597

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Scopus

Statistical survey of Arase satellite data sets in conjunction with the Finnish Riometer Network Reviewed Open Access

Neethal Thomas, Antti Kero, Yoshizumi Miyoshi, Kazuo Shiokawa, Miikka Hyötylä, Tero Raita, Yoshiya Kasahara, Iku Shinohara, Shoya Matsuda, Satoko Nakamura, Satoshi Kasahara, Shoichiro Yokota, Kunihiro Keika, Tomoaki Hori, Takefumi Mitani, Takeshi Takashima, Kazushi Asamura, Yoichi Kazama, Shiang‐Yu Wang, C‐W. Jun, Nana Higashio

Journal of Geophysical Research: Space Physics Vol. 127 ( 5 ) 2022.5

Simultaneous Observations of EMIC‐Induced Drifting Electron Holes (EDEHs) in the Earth's Radiation Belt by the Arase Satellite, Van Allen Probes, and THEMIS Reviewed Open Access

S. Nakamura, Y. Miyoshi, K. Shiokawa, Y. Omura, T. Mitani, T. Takashima, N. Higashio, I. Shinohara, T. Hori, S. Imajo, A. Matsuoka, F. Tsuchiya, A. Kumamoto, Y. Kasahara, M. Shoji, H. Spence, V. Angelopoulos

Geophysical Research Letters Vol. 49 ( 5 ) 2022.3

Detecting Equatorial Plasma Bubbles on All-Sky Imager Images Using Convolutional Neural Network Reviewed

Srisamoodkham W., Shiokawa K., Otsuka Y., Ansari K., Jamjareegulgarn P.

Lecture Notes in Networks and Systems Vol. 461 page： 481 - 487 2022

Language：English Publishing type：Research paper (scientific journal) Publisher：Lecture Notes in Networks and Systems

This paper proposes initially to apply convolutional neural network (CNN) for detecting the equatorial plasma bubbles on the ASI images. The considered CNN model is the YOLO v3 tiny model under a deep learning API (Keras), running on top of the machine learning platform (TensorFlow). Our program for EPB detection is written in Python that is extended easily to combine into a space weather web site for detecting and notifying EPBs in our next step. The results show that the YOLO v3-based CNN can detect the EPBs in ASI images with different intensities obtained from many countries. The threshold is tested and selected to be 0.40 suitably for detecting the anomaly (EPB existence). The maximum anomalous value is selected to decide the EPB occurrence.

DOI： 10.1007/978-981-19-2130-8_38

Scopus

Variations of Zonal Wind Velocity in the Thermosphere Observed at Southeast Asian Sector During Quiet and Active Geomagnetic Days Reviewed

Sarudin Idahwati, Hamid Nurul Shayana Abdul, Abdullah Mardina, Rusli Fatin Nur Syakirah Mohd, Otsuka Yuichi, Shiokawa Kazuo, Yatini Clara, Komonjinda Siramas, Somboon Ekkarach

JURNAL FIZIK MALAYSIA Vol. 43 ( 1 ) page： 10025 - 10035 2022

Spatio-Temporal Distributions of Lightning Stroke Charge Using ELF and Meteorological Data Reviewed

Yasuhide Hobara, Takuhiko Ohashi, Tomonori Shiraishi, Kazuo Shiokawa

Lecture Notes in Electrical Engineering Vol. 842 page： 329 - 337 2022

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

In this paper lightning stroke charges are estimated remotely by using combinations of Extremely Low Frequency (ELF) radio waves, conventional Lightning Locating System (LLS) and local meteorological information for the first time. Each lightning stroke location from LLS and corresponding transient signature of ELF magnetic field observed at a long distance (−1000 km between lightning stroke and observation site) are utilized to estimate the charge moment change (CMC) of the lightning stroke. The lightning stroke charge Q is then derived by dividing the CMC by the altitude of the neutralized lightning charge. The corresponding altitude of the neutralized lightning charge for each stroke is determined by assuming local −20 °C altitude for a positive stroke (−10 °C altitude for a negative strokes) from MesoScale Model (MSM). Spatial and temporal frequency distributions of energetic lightning (large amount of stroke charge) and cumulative frequency distributions of stroke charge in northwestern part of Japan in local summer and winter seasons for 4 years were derived. The spatial occurrence frequency distributions indicate that lightning strokes with a large amount of neutralized charge occur more frequently in inland areas during summertime and in coastal areas in winter. The cumulative frequency distribution indicates that positive polarity lightning strokes in winter tend to have a large charge. Our statistical results are in good agreement with the lightning properties inferred from local observations, and are considered to be useful information not only to study electrical properties of thunderstorms but also for future maintenance planning of power grid systems in wide areas and mitigation of lightning damages.

DOI： 10.1007/978-981-16-8690-0_30

Scopus

RESPONSE OF THE D-REGION IONOSPHERE TO FIREBALLS USING VLF/LF TRANSMITTER SIGNALS Reviewed Open Access

Takeru Suzuki, Hiroyo Ohya, Fuminori Tsuchiya, Kazuo Shiokawa, Hiroyuki Nakata

18th Annual Meeting of the Asia Oceania Geosciences Society page： 215 - 217 2022

Horizontal Inhomogeneity in the D-Region Ionosphere During an X-Class Solar Flare Determined by OCTAVE VLF Observations Reviewed

Masaharu Nakayama, Hiroyo Ohya, Fuminori Tsuchiya, Kenro Nozaki, Kazuo Shiokawa, Hiroyuki Nakata

URSI Radio Science Letters Vol. 4 2022

Spatio-Temporal Characteristics of Energetic Lightning in Southeast Asia: Preliminary Statistical Results Reviewed

Shunsuke Akama, Yasuhide Hobara, Amir Izzani Mohamed, Chandima Gomes, Kazuo Shiokawa, Shu Hirai, Hiroshi Kikuchi, Michael Stock

Lecture Notes in Electrical Engineering Vol. 842 page： 317 - 327 2022

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

The region of Southeast Asia is known as one of the lightning-prone areas in the world. However, spatial and temporal distributions of high-energy lightning discharges, which cause natural disasters e.g. significant damages to local power grid systems and forest fires, are still unknown. This paper reports initial results on the statistical characteristics of energetic lightning around Malay Peninsula. Highly accurate timing and location as well as lightning peak current (Ip ) of lightning strokes were obtained by ENTLN (Earth Networks Total Lightning Network), while the vertical charge moment change Qds as a proxy of high-energy lightning was derived by using ground-based ELF magnetic field observations in Pahang, Malaysia with a small threshold of less than 10 C·km. The characteristics of energetic lightning for both rainy and dry seasons were successfully derived for the first time in this region. The results indicate that highly energetic lightning occur frequently throughout the rainy and dry seasons, mainly over the Malacca Strait. Long-term statistical analysis with an extended data analysis period is necessary to understand further the seasonal and yearly dependences of energetic lightning and their relations with local climate conditions.

DOI： 10.1007/978-981-16-8690-0_29

Scopus

Predictability of variable solar-terrestrial coupling Reviewed Open Access

Daglis Ioannis A., Chang Loren C., Dasso Sergio, Gopalswamy Nat, Khabarova Olga V, Kilpua Emilia, Lopez Ramon, Marsh Daniel, Matthes Katja, Nandy Dibyendu, Seppala Annika, Shiokawa Kazuo, Thieblemont Remi, Zong Qiugang

ANNALES GEOPHYSICAE Vol. 39 ( 6 ) page： 1013 - 1035 2021.12

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

In October 2017, the Scientific Committee on Solar-Terrestrial Physics (SCOSTEP) Bureau established a committee for the design of SCOSTEP's Next Scientific Programme (NSP). The NSP committee members and authors of this paper decided from the very beginning of their deliberations that the predictability of the Sun-Earth System from a few hours to centuries is a timely scientific topic, combining the interests of different topical communities in a relevant way. Accordingly, the NSP was christened PRESTO -PREdictability of the variable Solar-Terrestrial cOupling. This paper presents a detailed account of PRESTO; we show the key milestones of the PRESTO roadmap for the next 5 years, review the current state of the art and discuss future studies required for the most effective development of solar-terrestrial physics.

DOI： 10.5194/angeo-39-1013-2021

Open Access

Web of Science

Scopus

Auroral Heating of Plasma Patches Due to High-Latitude Reconnection Reviewed

Pena Joaquin Diaz, Semeter Joshua, Nishimura Yukitoshi, Varney Roger, Reimer Ashton, Hairston Marc, Zettergren Matthew, Hirsch Michael, Verkhoglyadova Olga, Hosokawa Keisuke, Shiokawa Kazuo

JOURNAL OF GEOPHYSICAL RESEARCH-SPACE PHYSICS Vol. 126 ( 12 ) 2021.12

Language：English Publishing type：Research paper (scientific journal) Publisher：Journal of Geophysical Research: Space Physics

This study exploits the volumetric sampling capabilities of the Resolute Bay Incoherent Scatter Radar (RISR-N) in collaboration with all-sky imagery and in situ measurements to examine the interplay between cold plasma transport and auroral precipitation during a high-latitude lobe reconnection event on the dawn side. Solar wind IMF preceding the event was characterized by an impulsive negative excursion in Bz embedded within a period of Bz > 0 and By < 0. The combined effects of transport and magnetic stress release associated with a high-latitude reconnection pulse drove a co-mingling between patches and soft electron precipitation, creating common regions of elevated electron density and temperature. Vertical ionospheric profiles extracted in the rest frame of the drifting patch showed a contemporaneous increase in Te above 200 km and Ne below 250 km while at the same time showing only a small impact in Ne near the F-region peak. The observations suggest a new mechanism for creating a “hot patch” wherein the density enhancement is not generated by the precipitation but is warmed by it. The physics-based GEMINI model was used to explore the response to the observed precipitation as a function of altitude and time. Model results suggest that a correlated enhancement in Ne and Te at DMSP altitudes (∼800 km), that is, hot patch, can be produced by auroral heating and upward diffusion, irrespective of lower altitude density structure. The study highlights the need for densely distributed observations in space and time for understanding both mesoscale and small-scale ionospheric dynamics in regions subject to complex forcing.

DOI： 10.1029/2021JA029657

Web of Science

Scopus

Study of an Equatorward Detachment of Auroral Arc From the Oval Using Ground‐Space Observations and the BATS‐R‐US–CIMI Model Reviewed Open Access

Sneha Yadav, K. Shiokawa, S. Oyama, Y. Inaba, N. Takahashi, K. Seki, K. Keika, Tzu‐Fang Chang, S. W. Y. Tam, B.‐J. Wang, Y. Kazama, S.‐Y. Wang, K. Asamura, S. Kasahara, S. Yokota, T. Hori, Y. Kasaba, F. Tsuchiya, A. Kumamoto, M. Shoji, Y. Kasahara, A. Matsuoka, S. Matsuda, C.‐W. Jun, S. Imajo, Y. Miyoshi, I. Shinohara

Journal of Geophysical Research: Space Physics Vol. 126 ( 12 ) 2021.12

Multipoint Measurement of Fine‐Structured EMIC Waves by Arase, Van Allen Probe A, and Ground Stations Reviewed Open Access

S. Matsuda, Y. Miyoshi, Y. Kasahara, L. Blum, C. Colpitts, K. Asamura, Y. Kasaba, A. Matsuoka, F. Tsuchiya, A. Kumamoto, M. Teramoto, S. Nakamura, M. Kitahara, I. Shinohara, G. Reeves, H. Spence, K. Shiokawa, T. Nagatsuma, S. Oyama, I. R. Mann

Geophysical Research Letters Vol. 48 ( 23 ) 2021.11

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Papers - SHIOKAWA, Kazuo