Magnetic Reconnection under a Relativistic Drift Current

2023 Fiscal Year Final Research Report

• Project/Area Number: 20K20908
• Research Category: Grant-in-Aid for Challenging Research (Exploratory)
• Allocation Type: Multi-year Fund
• Review Section: Medium-sized Section 14:Plasma science and related fields
• Research Institution: The University of Tokyo
• Principal Investigator: Hoshino Masahiro 東京大学, 大学院理学系研究科(理学部), 教授 (90241257)
• Project Period (FY): 2020-07-30 – 2024-03-31
• Keywords: 宇宙プラズマ / 磁気リコネクション / 粒子加速 / プラズマ加熱

Outline of Final Research Achievements

Magnetic reconnection has been studied for more than 70 years as a ubiquitous plasma process that converts magnetic field energy into plasma kinetic energy, and recently its scope has been extended to the relativistic plasma regime, including applications to high-energy astronomical phenomena. Two different aspects of relativistic reconnection, relativistic high temperature plasmas and relativistic high drift velocity, have been investigated in this research project. In the first half of the research period, we studied the dependence on the drift speed and found that the growth rate decreases when the drift speed asymptotically approaches the speed of light and the Lorentz factor exceeds about 2. In the second half of the research period, the energy partitioning problem of relativistic reconnection was studied in terms of the efficiency of thermal plasma production and non-thermal particle acceleration.

Free Research Field

宇宙惑星プラズマ物理学

Academic Significance and Societal Importance of the Research Achievements

磁気リコネクションの研究は、磁場のトポロジー変化に伴い磁場エネルギーを急激に解放するメカニズムとして、実験室プラズマから宇宙プラズマまで数多くの研究が行われてきている。本研究は、極限宇宙を解明するために欠かせないリコネクションによる磁気エネルギー散逸率および散逸した結果のエネルギー分配問題に焦点を当てて研究を行った。パルサー磁気圏やブラックホール磁気圏を始めとする高エネルギー天体のプラズマ環境を理解するうえで重要な結果を得た。