Study on the dayside boundary layer of a small-scale magnetosphere by full-particle model computer experiments

2021 Fiscal Year Final Research Report

• Project/Area Number: 16H04058
• Research Category: Grant-in-Aid for Scientific Research (B)
• Allocation Type: Single-year Grants
• Section: 一般
• Research Field: Space and upper atmospheric physics
• Research Institution: Kobe University
• Principal Investigator: USUI HIDEYUKI 神戸大学, システム情報学研究科, 教授 (10243081)
• Project Period (FY): 2016-04-01 – 2020-03-31
• Keywords: 小型磁気圏 / 磁気圏境界層 / プラズマ粒子シミュレーション / 月惑星プラズマ / 粒子速度分布関数 / 月面磁気異常 / 水星磁気圏

Outline of Final Research Achievements

In the dayside boundary layer of a small-scale magnetosphere, an electric field is formed due to the difference in the motion of solar wind electrons and ions, and the formation of a non-thermal component due to electron acceleration is revealed. Plasma simulations with the electron beam are performed, and it is suggested that the density disturbance and electric field excitation in the boundary layer can be caused by current-driven plasma instabilities. Next, hybrid particle simulations are performed to investigate the density, magnetic field, and current in the dayside boundary layer of Mercury's magnetosphere. The meandering motion of solar wind ions in the dayside boundary layer is clarified, and it is shown in three dimensions that the dayside boundary is in direct contact with the Mercury surface when the solar wind dynamic pressure is higher than the magnetic pressure in the Mercury magnetosphere.

Free Research Field

宇宙環境シミュレーション科学

Academic Significance and Societal Importance of the Research Achievements

国際月探査計画アルテミスや日欧を中心とした国際水星探査計画BepiColomboにより月や水星の小型磁気圏探査が本格的に実施される。これらに先立ち、宇宙空間プラズマシミュレーションにより小型磁気圏物理現象をできる限り明らかにすることは学術的に重要であるとともに、月惑星ミッションで得られる観測データの物理解釈に大きな手助けとなる。特に、これら磁気圏は地球のものより小さいため磁気圏物理において特に太陽風プラズマの運動論的効果が重要となる。その効果に着目した本研究の結果は小型磁気圏物理の理解に貴重な知見を与える。