Study on spatio-temporal variations of oxygen ring current enhancements during magnetic storms using multi-spacecraft observations

• Project/Area Number: 17K14400
• Research Category: Grant-in-Aid for Young Scientists (B)
• Allocation Type: Multi-year Fund
• Research Field: Space and upper atmospheric physics
• Research Institution: The University of Tokyo
• Principal Investigator: Keika Kunihiro 東京大学, 大学院理学系研究科(理学部), 助教 (10719454)
• Project Period (FY): 2017-04-01 – 2020-03-31
• Project Status: Completed (Fiscal Year 2019)
• Budget Amount: ¥3,770,000 (Direct Cost: ¥2,900,000、Indirect Cost: ¥870,000); Fiscal Year 2019: ¥1,170,000 (Direct Cost: ¥900,000、Indirect Cost: ¥270,000); Fiscal Year 2018: ¥1,430,000 (Direct Cost: ¥1,100,000、Indirect Cost: ¥330,000); Fiscal Year 2017: ¥1,170,000 (Direct Cost: ¥900,000、Indirect Cost: ¥270,000)
• Keywords: 地球磁気圏 / 磁気嵐 / 環状電流 / 地球起源酸素イオン / 重イオン選択的加速 / サブストーム / リングカレント / 電離圏起源イオン / イオン輸送、加速 / あらせ衛星 / 酸素イオン / 多点観測 / あらせ（ERG）衛星

Outline of Final Research Achievements

This study investigated spatial variations and energy-spectral evolution of oxygen ions of atmospheric origin in the inner magnetosphere (called geospace, at altitudes up to ~50,000 km), using in-situ observations made by multiple spacecraft such as Van Allen Probes and ERG (Arase). The oxygen ions make a significant contribution to ion pressure enhancements during magnetic storms. The observations showed that oxygen ions behave similarly to protons in the deep inner magnetosphere. Near the magnetotail, on the other hand, oxygen ions are energized more effectively than protons. The results indicate that oxygen ions are preferentially accelerated in the magnetotail and that the kinetic process affects plasma characteristics in the inner magnetosphere.

Academic Significance and Societal Importance of the Research Achievements

今回の研究成果である水素イオンと酸素イオンのエネルギー化の相違は、磁気圏近尾部のグローバルダイナミクスが流体近似では説明できないことを示している。地球半径の数倍以上の空間スケールを持つ現象に対する、プラズマの数kmから数千kmスケールの粒子的振る舞いの重要性に一石を投じた。
また酸素イオン圧力は、磁気嵐の規模が大きいほど増加量が多いと言われている。酸素イオンの振る舞い（輸送や加速）をより深く理解することは、人類の宇宙活動に密接な宇宙天気現象としての巨大磁気嵐の発生メカニズムを理解する上でも重要である。

Research Products

• [Int'l Joint Research] Johns Hopkins Univ. Applied Physics Lab./University of New Hampshire/Southwest Research Institute(米国)
• [Int'l Joint Research] Johns Hopkins Univ APL/University of California Los Angeles/Aerospace Corporation(米国)
• [Journal Article] Comprehensive Observations of Substorm‐Enhanced Plasmaspheric Hiss Generation, Propagation, and Dissipation (2020)
  • Author(s): Liu Nigang、Su Zhenpeng、Gao Zhonglei、Zheng Huinan、Wang Yuming、Wang Shui、Miyoshi Yoshizumi、Shinohara Iku、et al.
  • Journal Title: Geophysical Research Letters Volume: 47 Issue: 2
  • DOI: 10.1029/2019gl086040
  • Peer Reviewed / Open Access / Int'l Joint Research
• [Journal Article] Statistical study on electron and ion temperatures in the near-Earth reconnection and magnetic pile-up regions (2019)
  • Author(s): K. Watanabe, K. Keika, M. Hoshino, N. Kitamura, Y. Saito, B. L. Giles, and W. R. Paterson
  • Journal Title: Geophys. Res. Letters Volume: 46 Issue: 24 Pages: 14223-14229
  • DOI: 10.1029/2019gl084837
  • Peer Reviewed / Int'l Joint Research
• [Journal Article] Eastward propagating second harmonic poloidal waves triggered by temporary outward gradient of proton phase space density: Van Allen Probe A observation (2019)
  • Author(s): Yamamoto, K., M. Nose, K. Keika, D. P. Hartley, C. W. Smith, R. J. MacDowall, L. J. Lanzerotti, D. G. Mitchell, H. E. Spence, G. D. Reeves, J. R. Wygant, J. W. Bonnell, and S. Oimatsu
  • Journal Title: J. Geophys. Res. Volume: 124 Issue: 12 Pages: 1-20
  • DOI: 10.1029/2019ja027158
  • Peer Reviewed / Int'l Joint Research
• [Journal Article] Strong Diffusion of Energetic Electrons by Equatorial Chorus Waves in the Midnight‐to‐Dawn Sector (2019)
  • Author(s): Kasahara S.、Miyoshi Y.、Kurita S.、Yokota S.、Keika K.、Hori T.、Kasahara Y.、Matsuda S.、Kumamoto A.、Matsuoka A.、Seki K.、Shinohara I.
  • Journal Title: Geophysical Research Letters Volume: 46 Issue: 22 Pages: 12685-12692
  • DOI: 10.1029/2019gl085499
  • Peer Reviewed / Open Access / Int'l Joint Research
• [Journal Article] Cusp and Nightside Auroral Sources of O + in the Plasma Sheet (2019)
  • Author(s): Kistler L. M.、Mouikis C. G.、Asamura K.、Yokota S.、Kasahara S.、Miyoshi Y.、Keika K.、Matsuoka A.、Shinohara I.、Hori T.、Kitamura N.、Petrinec S. M.、Cohen I. J.、Delcourt D. C.
  • Journal Title: Journal of Geophysical Research: Space Physics Volume: 124 Issue: 12 Pages: 10036-10047
  • DOI: 10.1029/2019ja027061
  • Peer Reviewed / Int'l Joint Research
• [Journal Article] Statistical Properties of Molecular Ions in the Ring Current Observed by the Arase (ERG) Satellite (2019)
  • Author(s): Seki K.、Keika K.、Kasahara S.、Yokota S.、Hori T.、Asamura K.、Higashio N.、Takada M.、Ogawa Y.、Matsuoka A.、Teramoto M.、Miyoshi Y.、Shinohara I.
  • Journal Title: Geophysical Research Letters Volume: 46 Issue: 15 Pages: 8643-8651
  • DOI: 10.1029/2019gl084163
  • Peer Reviewed / Int'l Joint Research
• [Journal Article] EMIC waves converted from equatorial noise due to M/Q=2 ions in the plasmasphere: Observations from Van Allen Probes and Arase (2019)
  • Author(s): Miyoshi Y.、Matsuda S.、Kurita S.、Nomura K.、Keika K.、Shoji M.、Kitamura N.、Kasahara Y.、Matsuoka A.、Shinohara I.、Shiokawa K.、Machida S.、Santolik O.、Boardsen S.A.、Horne R.B.、Wygant J.F.
  • Journal Title: Geophysical Research Letters Volume: 29 April Issue: 11 Pages: 0-0
  • DOI: 10.1029/2019gl083024
  • Peer Reviewed / Open Access / Int'l Joint Research
• [Journal Article] Meridional Distribution of Middle‐Energy Protons and Pressure‐Driven Currents in the Nightside Inner Magnetosphere: Arase Observations (2019)
  • Author(s): Imajo S.、Nos? M.、Kasahara S.、Yokota S.、Matsuoka A.、Keika K.、Hori T.、Teramoto M.、Yamamoto K.、Oimatsu S.、Nomura R.、Fujimoto A.、Shinohara I.、Miyoshi Y.
  • Journal Title: Journal of Geophysical Research: Space Physics Volume: 124 Issue: 7 Pages: 5719-5733
  • DOI: 10.1029/2019ja026682
  • Peer Reviewed
• [Journal Article] Characteristics of CME‐ and CIR‐driven ion upflows in the polar ionosphere (2019)
  • Author(s): Y. Ogawa K. Seki K. Keika Y. Ebihara
  • Journal Title: Journal of Geophysical Research: Space Physics Volume: 124 Issue: 5 Pages: 3637-3649
  • DOI: 10.1029/2018ja025870
  • Peer Reviewed
• [Journal Article] Statistical study of selective oxygen increase in high‐energy ring current ions during magnetic storms (2019)
  • Author(s): Mitani, K., K. Seki, K. Keika, M. Gkioulidou, L. J. Lanzerotti, D. G. Mitchell, C. A. Kletzing, A. Yoshikawa, and Y. Obana
  • Journal Title: J. Geophys. Res. Volume: 124 Issue: 5 Pages: 3193-3209
  • DOI: 10.1029/2018ja026168
  • Peer Reviewed / Open Access / Int'l Joint Research
• [Journal Article] Ion energies dominating energy density in the inner magnetosphere: Spatial distributions and composition, observed by Arase/MEP-i (2018)
  • Author(s): Keika, K. S. Kasahara, S. Yokota, M. Hoshino, K. Seki, M. Nose, T. Amano, Y. Miyoshi, and I. Shinohara,
  • Journal Title: Geophysical Research Letters Volume: 45 Issue: 22 Pages: 12153-12162
  • DOI: 10.1029/2018gl080047
  • Peer Reviewed / Open Access / Int'l Joint Research
• [Journal Article] Magnetosphere-ionosphere connection of storm-time Region-2 field-aligned current and ring current: Arase and AMPERE observations (2018)
  • Author(s): S. Imajo, M. Nose, A. Matsuoka, S. Kasahara, S. Yokota, M. Teramoto, K. Keika, T. Motoba, B. Anderson, R. Nomura, A. Fujimoto, I. Shinohara, and Y. Miyoshi
  • Journal Title: J. Geophys. Res. Volume: 123 Issue: 11 Pages: 9545-9559
  • DOI: 10.1029/2018ja025865
  • Peer Reviewed / Int'l Joint Research
• [Journal Article] Giant pulsations excited by a steep earthward gradient of proton phase space density: Arase observation (2018)
  • Author(s): Yamamoto, K., M. Nose, S. Kasahara, S. Yokota, K. Keika, A. Matsuoka, M. Teramoto, K. Takahashi, S. Oimatsu, R. Nomura, M. Vellante, B. Heilig, A. Fujimoto, Y. Tanaka, M. Shinohara I. Shinohara, and Y. Miyoshi
  • Journal Title: Geophysical Research Letters Volume: 45 Issue: 14 Pages: 6773-6781
  • DOI: 10.1029/2018gl078293
  • Peer Reviewed / Int'l Joint Research
• [Journal Article] Drift‐bounce resonance between Pc5 pulsations and ions at multiple energies in the nightside magnetosphere: Arase and MMS observations (2018)
  • Author(s): Oimatsu, S., M. Nose, 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, and P.‐A. Lindqvist
  • Journal Title: Geophysical Research Letters Volume: 45 Issue: 15 Pages: 1-10
  • DOI: 10.1029/2018gl078961
  • Peer Reviewed / Int'l Joint Research
• [Journal Article] Magnetic field dipolarization and its associated ion flux variations in the dawnside deep inner magnetosphere: Arase observations (2018)
  • Author(s): Nose, M., 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, and Y. Miyoshi
  • Journal Title: Geophysical Research Letters Volume: 45 Issue: 16 Pages: 7942-7950
  • DOI: 10.1029/2018gl078825
  • Peer Reviewed / Open Access / Int'l Joint Research
• [Journal Article] Radial transport of higher-energy oxygen ions into the deep inner magnetosphere observed by Van Allen Probes (2018)
  • Author(s): K. Mitani, K. Seki, K. Keika, M. Gkioulidou, L. J. Lanzerotti, D. G. Mitchell, and C. A. Kletzing
  • Journal Title: Geophys. Res. Lett. Volume: 45 Issue: 10 Pages: 4534-4541
  • DOI: 10.1029/2018gl077500
  • Peer Reviewed / Open Access / Int'l Joint Research
• [Journal Article] Van Allen Probes observations of drift-bounce resonance and energy transfer between energetic ring current protons and poloidal Pc4 wave (2018)
  • Author(s): Oimatsu, S., M. Nose, K. Takahashi, K. Yamamoto, K. Keika, C. A. Kletzing, C. W. Smith, R. J. MacDowall, and D. G. Mitchell
  • Journal Title: J. Geophys. Res. Volume: 123 Issue: 5 Pages: 1-15
  • DOI: 10.1029/2017ja025087
  • Peer Reviewed / Open Access / Int'l Joint Research
• [Presentation] Ion Energization During Reconnection-driven Large-scale Injections in Saturn's Magnetotail: Cassini Observations (2020)
  • Author(s): K. Keika, P. C. Brandt, D. G. Mitchell, R. C. Allen, C. Paranicas, M. Kusterer, D. C. Hamilton, and S. Sakai
  • Organizer: Symposium on Planetary Sciences 2020
• [Presentation] Ion energization in the near-Earth magnetotail observed by Arase (2019)
  • Author(s): K. Keika, S. Kasahara, S. Yokota, M. Hoshino, K. Seki, T. Amano, L. M. Kistler, M. Nose', Y. Miyoshi, T. Hori, and I. Shinohara
  • Organizer: AGU Fall Meeting 2019
  • Int'l Joint Research
• [Presentation] Transport and energization of ionospheric ions in Earth's magnetotail: Recent multi-spacecraft observations (2019)
  • Author(s): K. Keika
  • Organizer: APPC 2019 14th Asia-Pacific Physics Conference
  • Int'l Joint Research / Invited
• [Presentation] Mass- and charge-dependent ion energization in Earth's magnetotail: Arase observations (2019)
  • Author(s): K. Keika, S. Kasahara, S. Yokota, M. Hoshino, K. Seki, T. Amano, L. M. Kistler, M. Nose', Y. Miyoshi, T. Hori, and I. Shinohara
  • Organizer: SGEPSS 2019 Fall Meeting
• [Presentation] Characteristics of ion kinetic energies dominating plasma pressure: Spatial distributions and mass dependence (2019)
  • Author(s): K. Keika
  • Organizer: Ion Composition of Sun-Earth System meeting 2019
  • Int'l Joint Research
• [Presentation] Warm proton populations in the magnetotail under quiet conditions: Statistical analysis based on two-component fits of distribution functions (2019)
  • Author(s): K. Keika, R. Asami, M. Hoshino, S. Fuselier, and MMS/HPCA team
  • Organizer: Ion Composition of Sun-Earth System meeting 2019
  • Int'l Joint Research
• [Presentation] Statistical study on warm plasma in the magnetotail based on two-component fits of distribution functions (2019)
  • Author(s): K. Keika, R. Asami, M. Hoshino, S. Fuselier, and MMS/HPCA team
  • Organizer: JpGU Meeting 2019
  • Int'l Joint Research
• [Presentation] Oxygen-proton differences in ion energies dominating plasma pressure: Dependence on storm phases and solar wind drivers (2019)
  • Author(s): K. Keika, S. Kasahara, S. Yokota, M. Hoshino, K. Seki, M. Nose', Y. Miyoshi, and I. Shinohara
  • Organizer: JpGU Meeting 2019
  • Int'l Joint Research
• [Presentation] Proton-Oxygen Differences in Energy Spectral Evolution During Large-scale Injections in Saturn's Magnetosphere (2019)
  • Author(s): K. Keika, P. C. Brandt, D.G. Mitchell, and S. Sakai
  • Organizer: SGEPSS 2019 Fall Meeting
• [Presentation] Spatio-temporal Evolution of Energy Spectra of Energetic Protons and Oxygen Ions During Large-scale Injections in Saturn's Magnetosphere (2019)
  • Author(s): K. Keika, P. C. Brandt, D. G. Mitchell, M. Kusterer, D. C. Hamilton, and S. Sakai
  • Organizer: Magnetospheres of Outer Planets 2019 Meeting
  • Int'l Joint Research
• [Presentation] Mass and Charge Dependent Characteristics of Earth’s Magnetospheric Plasma (2018)
  • Author(s): 桂華邦裕
  • Organizer: 2nd Asia-Pacific Conference on Plasma Physics
  • Int'l Joint Research / Invited
• [Presentation] Contribution from proton and oxygen ions to plasma pressure in the Earth’s inner magnetosphere: Arase (ERG) observations (2018)
  • Author(s): 桂華邦裕
  • Organizer: 2nd URSI AT-RASC meeting
  • Int'l Joint Research / Invited
• [Presentation] Spatial distribution of the contributions from electrons, protons, and oxygen ions to energy density in the inner magnetosphere (2018)
  • Author(s): 桂華邦裕
  • Organizer: JpGU 2018 meeting
  • Int'l Joint Research / Invited
• [Presentation] Contribution from oxygen ions to plasma pressure in the inner magnetosphere: Spatial distributions and contributing energies (2018)
  • Author(s): 桂華邦裕
  • Organizer: SGEPSS 2018 Fall Meeting
• [Presentation] Contribution from mass-dependent acceleration to the buildup of the ring current: Arase observations (2018)
  • Author(s): 桂華邦裕
  • Organizer: AGU Fall Meeting 2018
  • Int'l Joint Research
• [Presentation] Energy and mass dependence of the contribution to storm-time plasma pressure: Arase/MEP-i observations (2017)
  • Author(s): K. Keika, S. Kasahara, S. Yokota, M. Hoshino, K. Seki, M. Nose', T. Amano, Y. Miyoshi, I. Shinohara
  • Organizer: SGEPSS 2017 Fall Meeting
• [Presentation] Energy and mass dependence of the contribution to storm-time plasma pressure observed by Arase/MEP-i (2017)
  • Author(s): K. Keika, S. Kasahara, S. Yokota, M. Hoshino, K. Seki, M. Nose', T. Amano, Y. Miyoshi, I. Shinohara
  • Organizer: AGU 2017 Fall Meeting
  • Int'l Joint Research
• [Remarks] 東京大学理学系研究科地球惑星科学専攻
  • URL: http://www.eps.s.u-tokyo.ac.jp