地上－衛星観測に基づくホイッスラー波動による放射線帯電子消失過程の解明

• Project/Area Number: 14J09407
• Research Category: Grant-in-Aid for JSPS Fellows
• Allocation Type: Single-year Grants
• Section: 国内
• Research Field: Space and upper atmospheric physics
• Research Institution: Nagoya University
• Principal Investigator: 栗田 怜 名古屋大学, 宇宙地球環境研究所, 特別研究員(PD)
• Project Period (FY): 2014-04-25 – 2017-03-31
• Project Status: Completed (Fiscal Year 2016)
• Budget Amount: ¥4,420,000 (Direct Cost: ¥3,400,000、Indirect Cost: ¥1,020,000); Fiscal Year 2016: ¥1,430,000 (Direct Cost: ¥1,100,000、Indirect Cost: ¥330,000); Fiscal Year 2015: ¥1,430,000 (Direct Cost: ¥1,100,000、Indirect Cost: ¥330,000); Fiscal Year 2014: ¥1,560,000 (Direct Cost: ¥1,200,000、Indirect Cost: ¥360,000)
• Keywords: マイクロバースト / コーラス / 放射線帯 / 放射線帯電子加速 / ディフューズオーロラ / Van Allen Probes / SAMPEX / 脈動オーロラ / 昭和基地

Outline of Annual Research Achievements

地球磁気圏内で観測されるコーラス波動は、MeV帯電子の内部加速に寄与することが示唆されており、磁気嵐時の放射線帯外帯再形成に重要な役割を果たしていることが指摘されている。一方で、コーラス波動はマイクロバーストと呼ばれる放射線帯電子の消失を引き起こすことも知られている。
コーラスによる内部加速に起因するMeV電子フラックスの増大ととマイクロバーストによるMeV電子の消失のバランスに関して調べるため、磁気嵐時の放射線帯電子変動に対して、SAMPEXとVan Allen Probes衛星のデータを用いて 事例解析を行った。その結果、500 keVから数MeV帯の放射線帯電子が増加するのに対応して1MeV帯の電子の降り込みが増大していることがわかった。このことから、コーラス波動による加速は大気への降り込みによる消失に比べて極めて効率的であり、コーラスとの波動粒子相互作用の結果、正味として放射線帯電子は増加する傾向にあることが示唆された。
上記の事例解析の結果と数値実験の検証結果を統計的に調査するために、SAMPEX・Polar衛星の観測データを用いて、放射線帯電子フラックスの変動とマイクロバーストの発生頻度を調査した。その結果、放射線帯電子のフラックスが大きく増加する際にマイクロバーストの発生頻度が高くなることがわかった。一方で、放射線帯電子のフラックスが大きく減少するタイミングとマイクロバーストの発生頻度には顕著な関係性が見られなかった。
以上のことから、マイクロバーストは、コーラス波動によって放射線帯電子が加速される際の副産物であり、マイクロバーストによる放射線帯電子消失に対する寄与は放射線帯電子増加に比べて非常に小さいと考えられる。

Research Progress Status

28年度が最終年度であるため、記入しない。

Strategy for Future Research Activity

28年度が最終年度であるため、記入しない。

Research Products

• [Journal Article] Waves in the innermost open boundary layer formed by dayside magnetopause reconnection (2017)
  • Author(s): H. Uchino, S. Kurita, Y. Harada, S. Machida, V. Angelopoulos
  • Journal Title: Journal of Geophysical Research: Space Physics Volume: 印刷中 Issue: 3 Pages: 3291-3307
  • DOI: 10.1002/2016ja023300
  • Peer Reviewed / Int'l Joint Research / Acknowledgement Compliant
• [Journal Article] Relativistic electron microbursts and variations in trapped MeV electron fluxes during the 8–9 October 2012 storm: SAMPEX and Van Allen Probes observations (2016)
  • Author(s): Kurita, S., Y. Miyoshi, J. B. Blake, G. D. Reeves, and C. A. Kletzing
  • Journal Title: Geophysical Research Letter Volume: 43 Issue: 7 Pages: 3017-3025
  • DOI: 10.1002/2016gl068260
  • Peer Reviewed / Int'l Joint Research / Acknowledgement Compliant
• [Journal Article] Relativistic electron precipitations in association with diffuse aurora: Conjugate observation of SAMPEX and the all-sky TV camera at Syowa Station (2015)
  • Author(s): Kurita, S., A. Kadokura, Y. Miyoshi, A. Morioka, Y. Sato, and H. Misawa
  • Journal Title: Geophys. Res. Lett. Volume: 42 Issue: 12 Pages: 4702-4708
  • DOI: 10.1002/2015gl064564
  • Peer Reviewed / Int'l Joint Research
• [Journal Article] Relation between fine structure of energy spectra for pulsating aurora electrons and frequency spectra of whistler-mode chorus waves (2015)
  • Author(s): Miyoshi, Y., S. Saito, K. Seki, T. Nishiyama, R. Kataoka, K. Asamura, Y. Katoh, Y. Ebihara, T. Sakanoi, M. Hirahara, S. Oyama, S. Kurita, O. Santolik
  • Journal Title: J. Geophys. Res. Volume: 120 Issue: 9 Pages: 7728-7736
  • DOI: 10.1002/2015ja021562
  • Peer Reviewed / Open Access / Int'l Joint Research
• [Journal Article] Energetic electron precipitation associated with pulsating aurora: EISCAT and Van Allen Probe observation (2015)
  • Author(s): Y. Miyoshi, S. Oyama, S. Saito, S. Kurita, H. Fujiwara, R. Kataoka, Y. Ebihara, C. Kletzing, G. Reeves, O. Santolik, M. Clilverd, C. Rodger, E. Turunen, and F. Tsuchiya
  • Journal Title: J. Geophys. Res. Space Physics Volume: 120 Issue: 4 Pages: 1-13
  • DOI: 10.1002/2014ja020690
  • Peer Reviewed / Open Access
• [Journal Article] Observational evidence of electron pitch angle scattering driven by ECH waves (2014)
  • Author(s): Kurita, S., Y. Miyoshi, C. M. Cully,V. Angelopoulos, O. Le Contel, M. Hikishima, and H. Misawa
  • Journal Title: Geophys. Res. Lett. Volume: 41 Issue: 22 Pages: 8076-8081
  • DOI: 10.1002/2014gl061927
  • Peer Reviewed / Acknowledgement Compliant
• [Journal Article] Extended lunar precursor regions: Electron-wave interaction (2014)
  • Author(s): Harada, Y., J. S. Halekas, A. R. Poppe, S. Kurita, and J. P. McFadden
  • Journal Title: J. Geophys. Res. Space Physics Volume: 119 Issue: 11 Pages: 9160-9173
  • DOI: 10.1002/2014ja020618
  • Peer Reviewed
• [Presentation] Response of relativistic electron microbursts to the arrival of high speed solar wind streams (2016)
  • Author(s): Kurita, S., Y. Miyoshi, and J. B. Blake
  • Organizer: AGU 2016 fall meeting
  • Place of Presentation: San Francisco
  • Year and Date: 2016-12-12
  • Int'l Joint Research
• [Presentation] Relativistic electron microbursts during different solar wind drivers (2016)
  • Author(s): 栗田怜、三好由純、J. B. Blake
  • Organizer: 地球電磁気・地球惑星圏学会第140回講演会
  • Place of Presentation: 九州大学伊都キャンパス
  • Year and Date: 2016-11-20
• [Presentation] 太陽風大規模構造に対する相対論的電子マイクロバーストの応答 (2016)
  • Author(s): 栗田怜、三好由純
  • Organizer: 第１３回宇宙環境シンポジウム
  • Place of Presentation: 情報通信研究機構
  • Year and Date: 2016-11-01
• [Presentation] Relativistic electron microbursts and local acceleration of MeV electrons by chorus: SAMPEX and Van Allen Probes observations (2016)
  • Author(s): Kurita, S., Y. Miyoshi, J. B. Blake, G. D. Reeves, and C. A. Kletzing
  • Organizer: AOGS 2016
  • Place of Presentation: Beijing
  • Year and Date: 2016-07-31
  • Int'l Joint Research / Invited
• [Presentation] Response of relativistic electron microbursts to the arrival of high speed solar wind streams (2016)
  • Author(s): Kurita, S., Y. Miyoshi, J. B. Blake
  • Organizer: GEM Summer Workshop
  • Place of Presentation: Santa Fe
  • Year and Date: 2016-06-20
  • Int'l Joint Research
• [Presentation] Ground-based and satellite measurements of microburst during pulsating aurora (2016)
  • Author(s): Kurita, S
  • Organizer: Meeting sponsored by International Space Science Institute ”Pulsating aurora as a manifestation of nonlinear wave-particle interaction”
  • Place of Presentation: ISSI-Beijing
  • Year and Date: 2016-05-29
  • Int'l Joint Research / Invited
• [Presentation] Relativistic electron microbursts and local acceleration of MeV electrons by chorus: SAMPEX and Van Allen Probes observations (2016)
  • Author(s): 栗田怜、三好由純、 J. B. Blake, G. D. Reeves, and C. A. Kletzing
  • Organizer: 日本地球惑星科学連合2016年大会
  • Place of Presentation: 幕張メッセ
  • Year and Date: 2016-05-22
• [Presentation] Relativistic electron microbursts and flux variations of trapped MeV electrons: SAMPEX and Van Allen Probes observations (2015)
  • Author(s): Kurita, S., Y. Miyoshi, J. B. Blake, and G. D. Reeves
  • Organizer: AGU fall meeting 2015
  • Place of Presentation: San Francisco
  • Year and Date: 2015-12-14
  • Int'l Joint Research
• [Presentation] Relativistic electron microbursts and flux variations of trapped MeV electrons: SAMPEX and Van Allen Probes observations (2015)
  • Author(s): 栗田怜、三好由純、J. B. Blake, and G. D. Reeves
  • Organizer: ISAS Workshop: Magnetospheric Plasmas 2015
  • Place of Presentation: 東京工業大学
  • Year and Date: 2015-12-02
  • Int'l Joint Research
• [Presentation] 大振幅ホイッスラーモード波動の統計解析 (2015)
  • Author(s): 栗田怜, 三好由純
  • Organizer: 第138回地球電磁気・地球惑星圏学会
  • Place of Presentation: 東京大学
  • Year and Date: 2015-11-01
• [Presentation] Occurrence characteristics of relativistic electron microbursts in association with storms and substorms (2015)
  • Author(s): 栗田怜, 三好由純
  • Organizer: 日本地球惑星科学連合2015年大会
  • Place of Presentation: 幕張メッセ
  • Year and Date: 2015-05-24
• [Presentation] Relativistic electron flux variations in the radiation belts during magnetic storms observed at different altitudes (2015)
  • Author(s): Kurita S., Y. Miyoshi, and G. D. Reeves
  • Organizer: International Workshop on Energetic Particle Processes of the near-Earth Space
  • Place of Presentation: Paris
  • Year and Date: 2015-05-18
  • Int'l Joint Research
• [Presentation] THEMIS observation of rising tone chorus elements without a gap at half the gyrofrequency (2015)
  • Author(s): Kurita S.
  • Organizer: ERG mission science workshop 2015
  • Place of Presentation: Taiwan
  • Year and Date: 2015-04-09
  • Int'l Joint Research
• [Presentation] THEMIS衛星の観測に基づくホイッスラーモード・コーラス波動励起理論 の検証 (2015)
  • Author(s): 栗田怜
  • Organizer: 「波動粒子相互作用による粒子加速・輸送及び乱流」研究会
  • Place of Presentation: 名古屋大学
  • Year and Date: 2015-03-05 – 2015-03-06
• [Presentation] The Structure of Io Torus Inferred from ECH Wave Spectra Observed by Galileo (2015)
  • Author(s): Kurita, S., and H. Misawa
  • Organizer: 第16回惑星圏研究会
  • Place of Presentation: 東北大学
  • Year and Date: 2015-02-16 – 2015-02-18
• [Presentation] Sub-relativistic and relativistic electron precipitations above diffuse aurora: Conjugate observations of SAMPEX and the all sky TV camera at Syowa Station (2014)
  • Author(s): Kurita, S., A. Kadokura, Y. Miyoshi, Y. Sato, H. Misawa and A. Morioka
  • Organizer: AGU fall meeting 2014
  • Place of Presentation: Moscone Center, San Francisco, CA, USA
  • Year and Date: 2014-12-15 – 2014-12-19
• [Presentation] Relativistic Electron Precipitation in Association with Diffuse Aurora: Conjugate Observation of SAMPEX and the All Sky TV Camera at Syowa Station (2014)
  • Author(s): Kurita, S., A. Kadokura, Y. Miyoshi, Y. Sato, H. Misawa, and A. Morioka
  • Organizer: 12th International Conference on Substorms
  • Place of Presentation: Ise-shima Royal Hotel
  • Year and Date: 2014-11-10
• [Presentation] Relativistic Electron Precipitation in Association with Diffuse Aurora: Conjugate Observation of SAMPEX and the All Sky TV Camera at Syowa Station (2014)
  • Author(s): Kurita, S., A. Kadokura, Y. Miyoshi, Y. Sato, H. Misawa, and A. Morioka
  • Organizer: Asia Oceania Geosciences Society meeting 2014
  • Place of Presentation: Sapporo Ryal Hotel
  • Year and Date: 2014-07-28 – 2014-08-01
• [Presentation] THEMIS observation of rising tone chorus elements without a gap at half the electron gyrofrequency (2014)
  • Author(s): Kurita, S., Y. Katoh, Y. Omura, V. Angelopoulos, C. M. Cully, O. Le Contel, and H. Misawa
  • Organizer: GEM Summer workshop 2014
  • Place of Presentation: Renaissance Portsmouth Hotel & Conference Center, Portsmouth, Virginia, USA
  • Year and Date: 2014-06-15 – 2014-06-20
• [Presentation] ディフューズオーロラに伴う相対論的電子降り込み (2014)
  • Author(s): 栗田怜, 門倉昭, 三好由純, 佐藤由佳, 三澤浩昭, 森岡昭
  • Organizer: 日本地球惑星科学連合2015年大会
  • Place of Presentation: 横浜パシフィコ
  • Year and Date: 2014-04-28 – 2014-05-02
• [Funded Workshop] AGU fall meeting 2015 (2015)
  • Place of Presentation: San Francisco, CA, USA
  • Year and Date: 2015-12-14
• [Funded Workshop] International Workshop on Energetic Particle Processes of the near-Earth Space (2015)
  • Place of Presentation: Paris, France
  • Year and Date: 2015-05-18