中国科学技术大学学报 ›› 2020, Vol. 50 ›› Issue (9): 1218-1228.DOI: 10.3969/j.issn.0253-2778.2020.09.002

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无碰撞磁场重联中的磁岛

陆全明   

  1. 1.中国科学技术大学地球和空间科学学院中国科学院近地空间环境重点实验室,安徽合肥 230026; 2.中国科学院比较行星学卓越创新中心,安徽合肥 230026
  • 收稿日期:2020-08-16 修回日期:2020-09-15 出版日期:2020-09-30 发布日期:2020-09-30

Magnetic islands in collisionless magnetic reconnection

  1. 1.CAS Key Lab of Geospace Environment, School of Earth and Space Sciences, University of Science and Technology of China, Hefei 230026, China;2. CAS Center for Excellence in Comparative Planetology, Hefei 230026, China
  • Received:2020-08-16 Revised:2020-09-15 Online:2020-09-30 Published:2020-09-30
  • Contact: LU Quanming
  • About author:LU Quanming(corresponding author), male, born in 1969, PhD/Changjiang Distinguished Prof. He received his BS degree from Nanjing University in 1990, and his MS and PhD degrees from University of Science and Technology of China in 1993 and 1996, respectively. He had been a postdoctor from 1996-1998 at Shanghai Institute of Optics and Fine Mechanics, Chinese Academy of Sciences, and from 1998-2000 at Tsukuba University, Japan. He joined the faculty of University of Science and Technology of China as associate professor in the Department of Earth and Space Sciences in 2000. He was promoted to full professor in 2003. His research field has been focused on space plasma physics, and he has published more than 200 SCI papers in international high-level academic journals including Nature Physics, Nature Communications and Physical Review Letters. E-mail: qmlu@ustc.edu.cn

摘要: 在以下两个方面回顾了磁岛在无碰撞磁场重联中的作用:磁能到等离子体动能和热能的快速转化以及高能量电子的产生.重联的X点附近的电流片可能被拉伸并导致撕裂模不稳定性,并形成相互作用的次级磁岛.这种非稳态的磁场重联图像可以维持长时间的高重联率,进而有效地耗散磁能.电子可在磁岛内通过费米和betatron机制加速,也可在X点附近通过重联电场加速.磁岛间的相互作用可进一步加速电子.这些加速过程可导致高能量电子的幂律谱分布.

关键词: 无碰撞磁场重联, 磁岛, 耗散, 高能量电子

Abstract: The roles of magnetic islands were reviewed in two essential aspects of collisionless magnetic reconnection: are rapid dissipation from magnetic energy to plasma kinetic energy and generation of energetic electrons. The current sheet around the X line may be extended and unstable to the tearing mode instability. Secondary magnetic islands are generated and then consequentially interact each other in the extended current sheet. Such a nonstationary magnetic reconnection can maintain a large reconnection rate for a long time and efficiently dissipate magnetic energy. Electrons can be accelerated inside magnetic islands by Fermi and betatron mechanisms, as well as by reconnection electric field in the vicinity of the X line. The interaction of magnetic islands can result in further electron acceleration. These acceleration processes can make energetic electrons possess a power-law spectrum.

Key words: collisionless magnetic reconnection, magnetic islands, dissipate, energetic electron