磁岛合并研究

The process of the coalescence of magnetic islands

本文采用二维全粒子模拟来研究无碰撞等离子体中的磁岛合并过程.结果表明,磁岛合并分为两个阶段,在第一个阶段,两个磁岛因同向电流丝之间的吸引力而缓慢地相互靠近,在这个过程中,合并线附近的电子被面外电场加速,形成薄电流片,同时电流片两侧形成磁场堆积.第二个阶段为快速重联阶段,合并线附近的电磁场结构和以Harris电流片为初态的重联扩散区的电磁场结构很相似,其中最显著的特点为面外磁场的四极型结构.

In this paper, two-dimensional （2D） particle-in-cell （PIC） simulations are performed to investigate the coalescence process of magnetic islands in collisionless plasma. We find that the merging of magnetic islands have two stages. In the first stage, the two islands approach each other slowly due to the attractive force between the homodromous currents. The electrons around the merging line are accelerated by the out-of-plane electric field, and then a thin current sheet is formed, where the magnetic field is also piled up. In the second stage, the fast magnetic reconnection occurs in the thin current sheet around the merging line, and the resulted electromagnetic structures around the merging line are similar to those in reconnection diffusion region formed in a Harris current sheet, where the most characteristic is the quadrupole structure of the out-of-plane magnetic field.