衝突のない宇宙プラズマにおける双方向波粒子エネルギー伝達の直接測定

N Kitamura^1,2, M Kitahara³, M Shoji⁴

¹Institute of Space and Astronautical Science, Japan Aerospace Exploration Agency, Sagamihara, Japan. kitamura@eps.s.u-tokyo.ac.jp.

Science (New York, N.Y.)

|September 8, 2018

まとめ

プラズマ波は宇宙の粒子間でエネルギーを伝達します超高速測定では熱い陽子がエネルギーを波に変換しそれが地球の磁気圏のヘリウムイオンを加速します

科学分野:

プラズマ物理学
宇宙物理学
天体物理学

背景:

波粒子の相互作用は,衝突のないプラズマにおけるエネルギーとモメンタムの交換に不可欠です.
これらの相互作用は,地球の磁気圏を含む宇宙環境で至る所に存在します.

研究の目的:

電磁イオンサイクロトロン波に関連した波粒子の相互作用におけるエネルギー伝達を定量的に評価する.
プラズマの異なる粒子集団間の衝突のないエネルギー伝送の直接的な証拠を提供すること.

主な方法:

地球の磁気圏内の磁気圏マルチスケール (MMS) 宇宙船からの超高速測定を用いた.
分析されたイオン分布とプラズマ波場との相関係.

主要な成果:

観測されたイオン分布は非対称で,プラズマ波場と相性であった.
熱い陽子から電磁離子サイクロトロン波にエネルギーを移した.
冷たいHe+イオンは波によって2キロ電子ボルトまでのエネルギーに非共振的に加速された.

結論:

異なる粒子集団間の衝突のないエネルギー伝達の直接的な定量的な証拠が波-粒子相互作用によって得られた.
地球の磁気圏におけるエネルギーの移転を媒介する電磁イオンサイクロトロン波の役割を実証した.
宇宙におけるプラズマダイナミクスの波粒子の相互作用を理解することの重要性を強調した.

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