大規模運動論的シミュレーションで解き明かす内部磁気圏の物理素過程

• Project Area: Solar-Terrestrial Environment Prediction as Science and Social Infrastructure
• Project/Area Number: 16H01170
• Research Category: Grant-in-Aid for Scientific Research on Innovative Areas (Research in a proposed research area)
• Allocation Type: Single-year Grants
• Review Section: Science and Engineering
• Research Institution: The University of Tokyo
• Principal Investigator: 天野 孝伸 東京大学, 大学院理学系研究科(理学部), 准教授 (00514853)
• Project Period (FY): 2016-04-01 – 2018-03-31
• Project Status: Completed (Fiscal Year 2017)
• Budget Amount: ¥3,380,000 (Direct Cost: ¥2,600,000、Indirect Cost: ¥780,000); Fiscal Year 2017: ¥1,690,000 (Direct Cost: ¥1,300,000、Indirect Cost: ¥390,000); Fiscal Year 2016: ¥1,690,000 (Direct Cost: ¥1,300,000、Indirect Cost: ¥390,000)
• Keywords: 地球磁気圏 / 無衝突プラズマ / プラズマ波動 / プラズマ不安定性 / 数値シミュレーション / 環電流 / 磁気嵐 / 磁気圏 / リングカレント / 波動 / 磁気圏・電離圏 / 超高層物理学

Outline of Annual Research Achievements

地球の内部磁気圏領域は平均的には双極子磁場の支配的な低ベータ領域であるが，磁気嵐時などにはプラズマシートからのプラズマ供給によって，リングカレント粒子のプラズマ圧が磁気圧と同程度になることが分かっており，このような場合のプラズマダイナミクスを調べるのが本研究の大きな目的である．特に，内部磁気圏領域での低周波磁気流体(MHD)波動(ULF波動)の起源として考えられてきたプラズマ不安定性の理解を目指し，背景プラズマをMHDとし，リングカレント粒子のみを運動論的に扱う独自開発の数値シミュレーションモデルを用いて研究を行った．

内部磁気圏を模擬したモデルとして，磁力線の曲率を無視したスラブ配位のもとで，磁気圧とリングカレント成分のプラズマ圧力がバランスした平衡状態を初期条件とした数値シミュレーションを実施した．ここでリングカレント成分に温度異方性(Tperp > Tpara)を与えた場合は，パラメータによってミラー不安定性と電磁イオンサイクロトロン(EMIC)不安定性が励起され得る．ただし，本研究で考えるパラメータ領域ではEMIC不安定性の方がミラー不安定性よりも優勢である．ところが，初期にミラー不安定性の条件を満たさない場合であってもミラー不安定性に特徴的な磁気圧とプラズマ圧の負相関が現れることがシミュレーション結果から分かった．シミュレーションで得られた分布関数データの解析から，これは初期にEMIC不安定性によって励起されたAlfven波によるピッチ角散乱がbi-Maxwellian分布とは異なる分布を形成し，これがミラー不安定性に対する運動論的な不安定条件を満たすことが分かった．今後はこの過程が起こる条件，特に磁気圏物理への適用可能性について議論を進めていく予定である．

Research Progress Status

29年度が最終年度であるため、記入しない。

Strategy for Future Research Activity

29年度が最終年度であるため、記入しない。

Research Products

• [Journal Article] A generalized quasi-neutral fluid-particle hybrid plasma model and its application to energetic-particle-magnetohydrodynamics hybrid simulation (2018)
  • Author(s): Amano Takanobu
  • Journal Title: Journal of Computational Physics Volume: 366 Pages: 366-385
  • DOI: 10.1016/j.jcp.2018.04.020
  • Peer Reviewed
• [Journal Article] Precursor Wave Emission Enhanced by Weibel Instability in Relativistic Shocks (2018)
  • Author(s): Iwamoto, M., Amano, T., Hoshino, M., Matsumoto, Y.
  • Journal Title: The Astrophysical Journal Volume: 印刷中
  • Peer Reviewed
• [Journal Article] Theory, modeling, and integrated studies in the Arase (ERG) project (2018)
  • Author(s): Seki Kanako、Miyoshi Yoshizumi、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
  • Journal Title: Earth, Planets and Space Volume: 70 Issue: 1 Pages: 17-17
  • DOI: 10.1186/s40623-018-0785-9
  • NAID: 120006517789
  • Peer Reviewed / Open Access / Int'l Joint Research
• [Journal Article] Formation of butterfly pitch angle distributions of relativistic electrons in the outer radiation belt with a monochromatic Pc5 wave (2018)
  • Author(s): Kamiya, K. Seki, K. Saito, S. Amano, T. Miyoshi, Y.
  • Journal Title: Journal of Geophysical Research Volume: 印刷中
  • Peer Reviewed
• [Journal Article] Electron Surfing and Drift Accelerations in a Weibel-Dominated High-Mach-Number Shock (2017)
  • Author(s): Matsumoto Yosuke、Amano Takanobu、Kato Tsunehiko N.、Hoshino Masahiro
  • Journal Title: Physical Review Letters Volume: 119 Issue: 10 Pages: 105101-105101
  • DOI: 10.1103/physrevlett.119.105101
  • NAID: 120007088133
  • Peer Reviewed
• [Journal Article] Electron Scattering by High-frequency Whistler Waves at Earth’s Bow Shock (2017)
  • Author(s): Oka M.、III L. B. Wilson、Phan T. D.、Hull A. J.、Amano T., et al. (全24名)
  • Journal Title: The Astrophysical Journal Volume: 842 Issue: 2 Pages: L11-L11
  • DOI: 10.3847/2041-8213/aa7759
  • Peer Reviewed / Int'l Joint Research
• [Journal Article] Persistence of Precursor Waves in Two-dimensional Relativistic Shocks (2017)
  • Author(s): Iwamoto Masanori、Amano Takanobu、Hoshino Masahiro、Matsumoto Yosuke
  • Journal Title: The Astrophysical Journal Volume: 840 Issue: 1 Pages: 52-52
  • DOI: 10.3847/1538-4357/aa6d6f
  • Peer Reviewed
• [Journal Article] Persistence of precursor waves in two-dimensional relativistic shocks (2017)
  • Author(s): Iwamoto, M., Amano, T., Hoshino, M., Matsumoto, T.
  • Journal Title: Astrophys. J. Volume: 印刷中
  • Peer Reviewed
• [Journal Article] A second-order divergence-constrained multidimensional numerical scheme for relativistic two-fluid electrodynamics (2016)
  • Author(s): Amano, T.
  • Journal Title: Astrophys. J. Volume: 831 Issue: 1 Pages: 100-100
  • DOI: 10.3847/0004-637x/831/1/100
  • Peer Reviewed / Acknowledgement Compliant
• [Journal Article] A High-order Relativistic Two-fluid Electrodynamic Scheme with Consistent Reconstruction of Electromagnetic Fields and A Multidimensional Riemann Solver for Electromagnetism (2016)
  • Author(s): Balsara, D., Amano, T., Garain, S., Kim, J.
  • Journal Title: J. Comput. Phys. Volume: 318 Pages: 169-200
  • DOI: 10.1016/j.jcp.2016.05.006
  • Peer Reviewed / Int'l Joint Research
• [Journal Article] A new framework for magnetohydrodynamic simulations with anisotropic pressure (2016)
  • Author(s): Hirabayashi, K., Hoshino, M., Amano, T.
  • Journal Title: J. Comput. Phys. Volume: 327 Pages: 851-872
  • DOI: 10.1016/j.jcp.2016.09.064
  • Peer Reviewed
• [Presentation] Astrophysical Coherent Radiation and Acceleration of Cosmic Rays (2018)
  • Author(s): Amano, T., Iwamoto, M., Matsumoto, Y., Hoshino, M.
  • Organizer: The 3rd STEPS Symposium on Photon Science, Mowcow, Russia
  • Int'l Joint Research
• [Presentation] Particle Acceleration in Relativistic Plasmas (2018)
  • Author(s): Amano, T.
  • Organizer: Dawn of a New Era for Black Hole Jets in Active Galaxies, Sendai, Japan
  • Int'l Joint Research / Invited
• [Presentation] 宇宙空間衝撃波の遷移層 (2018)
  • Author(s): 天野孝伸
  • Organizer: 日本物理学会 春季年会, 東京理科大学野田キャンパス
  • Invited
• [Presentation] Nonthermal Electrons at Quasi-perpendicular Collisionless Shocks (2017)
  • Author(s): Amano, T., Matsumoto, Y., Kato, T. N., Hoshino, M.
  • Organizer: 7th East-Asia Workshop on Laboratory, Space, Astrophysical Plasmas, Weihai, China
  • Int'l Joint Research / Invited
• [Presentation] Coherent and Stochastic Acceleration in Quasi-perpendicular Collisionless Shocks (2017)
  • Author(s): Amano, T., Matsumoto, Y., Kato, T. N., Hoshino, M.
  • Organizer: Workshop on Plasma Astrophysics from the Laboratory to the Non-thermal Universe, Oxford, UK
  • Int'l Joint Research / Invited
• [Presentation] Energetic Particle Hybrid Code and Its Application (2016)
  • Author(s): Amano, T.
  • Organizer: 11th International Conference on Numerical Modeling of Space Plasma Flows (ASTRONUM2016)
  • Place of Presentation: Monterey, USA
  • Int'l Joint Research / Invited
• [Presentation] Key Issues in Particle Acceleration Theory at Collisionless Shocks (2016)
  • Author(s): Amano, T.
  • Organizer: 18th International Congress on Plasma Physics
  • Place of Presentation: Kaohsiung, Taiwan
  • Int'l Joint Research / Invited
• [Presentation] Particle Acceleration and Transport at Collisionless Shocks (2016)
  • Author(s): Amano, T.
  • Organizer: 6th East-Asia Workshop on Laboratory, Space, Astrophysical Plasmas
  • Place of Presentation: Tsukuba, Ibaraki, Japan
  • Int'l Joint Research / Invited
• [Presentation] Kinetic Simulations of Particle Acceleration and Transport around Collisionless Shocks (2016)
  • Author(s): Amano, T.
  • Organizer: AOGS 13th Annual Meeting
  • Place of Presentation: Beijing, China
  • Int'l Joint Research / Invited
• [Presentation] 宇宙プラズマのハイブリッドシミュレーション (2016)
  • Author(s): 天野孝伸
  • Organizer: 日本物理学会 2016秋季年会
  • Place of Presentation: 金沢大学(石川県金沢市)
  • Invited