Study on three-dimensional magnetic reconnection based on formation-flying spacecraft observations of the magnetosphere

2018 Fiscal Year Final Research Report

• Project/Area Number: 15K05306
• Research Category: Grant-in-Aid for Scientific Research (C)
• Allocation Type: Multi-year Fund
• Section: 一般
• Research Field: Space and upper atmospheric physics
• Research Institution: Japan Aerospace EXploration Agency
• Principal Investigator: Hasegawa Hiroshi 国立研究開発法人宇宙航空研究開発機構, 宇宙科学研究所, 助教 (50435799)
• Research Collaborator: NAKAMURA takuma ; SONNERUP bengt
• Project Period (FY): 2015-04-01 – 2019-03-31
• Keywords: 磁気リコネクション / 磁気圏界面 / 磁気圏尾部 / 電子拡散領域 / 電子電磁流体力学

Outline of Final Research Achievements

Based on in-situ measurements by spacecraft of plasma and electromagnetic field, we studied the magnetic reconnection process in the geospace that plays a pivotal role in the transport of solar wind into Earth's magnetosphere and energy release during auroral expansion. We found that magnetic reconnection at the outer boundary of the magnetosphere, called the magnetopause, lasts for more than 5 hours along a line exceeding 70000 km, the largest-scale reconnection ever observed in the magnetosphere. Moreover, we successfully visualized multi-dimensional structures of the central small-scale region of magnetic reconnection observed in both the magnetopause and magnetotail.

Free Research Field

惑星間空間物理学

Academic Significance and Societal Importance of the Research Achievements

太陽風プラズマやエネルギーの地球磁気圏流入の原因である磁気圏界面の磁気リコネクションが、磁気圏内で発生しているオーロラ関連現象を説明できるほど大規模に起きていることを人工衛星による直接観測によって実証できたことに意義がある。また、目に見えない宇宙プラズマや磁場の観測データから、磁気リコネクションの中心領域を可視化し、磁力線がつなぎ変わる仕組みを理解することにつながるデータ解析手法を確立したことの意義は大きい。