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タイトル: | Generation of Field-Aligned Currents During Substorm Expansion: An Update |
著者: | Ebihara, Yusuke https://orcid.org/0000-0002-2293-1557 (unconfirmed) Tanaka, Takashi |
著者名の別形: | 海老原, 祐輔 |
キーワード: | substorm field-aligned current magnetosphere Alfven wave MHD simulation electric current |
発行日: | Feb-2023 |
出版者: | American Geophysical Union (AGU) |
誌名: | Journal of Geophysical Research: Space Physics |
巻: | 128 |
号: | 2 |
論文番号: | e2022JA031011 |
抄録: | We investigated generation processes of field-aligned currents (FACs) that are abruptly intensified at the beginning of the substorm expansion phase by tracing a packet of the Alfvén wave backward in time from the onset position in the ionosphere in the global magnetohydrodynamics (MHD) simulation. The generation region is found in the near-Earth plasma sheet, in which (a) azimuthally moving plasma pulls the magnetic field line, and performs negative work against the magnetic tension force to excite the Alfvén waves, (b) FACs are generated from the requirement of Ampère and Faraday laws, and (c) field-perpendicular current is converted to FACs. We call this near-Earth FAC dynamo. The plasma involved originates in the tail lobe region. When near-Earth reconnection occurs in the plasma sheet, the plasma is accelerated earthward by the Lorentz force, and decelerated by the plasma pressure gradient force, followed by the Lorentz force. The flow is deflected to the west and east directions by the plasma pressure gradient force and the Lorentz force, resulting in the excitation of Alfvén waves and FACs. The Alfvén waves propagate along the magnetic field in the rest frame of the moving plasma. When it arrives at the ionosphere, the auroral electrojet starts developing and the substorm expansion phase begins. The near-Earth FAC dynamo can be distinguished from the near-Earth dynamo (J · E < 0, where J is the current density and E is the electric field). We suggest that the evolution of the substorm can be understood in terms of the development of FACs. |
著作権等: | © 2023. The Authors. This is an open access article under the terms of the Creative Commons Attribution-NonCommercial-NoDerivs License, which permits use and distribution in any medium, provided the original work is properly cited, the use is non-commercial and no modifications or adaptations are made. |
URI: | http://hdl.handle.net/2433/282008 |
DOI(出版社版): | 10.1029/2022JA031011 |
出現コレクション: | 学術雑誌掲載論文等 |
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