地球远磁尾中的磁场重联（Ⅰ）流动撕裂模不稳定性

本文数值研究了地球远磁尾中流动撕裂模不稳定性所引起的磁场重联过程.结果表明,在短暂的指数增长之后,当磁岛宽度接近等离子体片厚度时,流动撕裂模不稳定性的增长率大大降低,最终磁岛宽度趋于饱和.磁岛的饱和宽度随着磁Reynolds数S的增大而减小,随着剪切流动层宽度δV的增大而增加.在S→∞的情况下,流动撕裂模将退化为流动颈缩模,磁场重联不再发生.当飞船通过由流动撕裂模不稳定性所形成的磁岛时,即可观测到磁场B_z分量由北转南或由南转北的现象.

MAGNETIC RECONNECTION IN THE EARTH'S DISTANT MAGNETOTAIL （I） STREAMING TEARING INSTABILITY

In this paper, a. magnetic reconnection proc .;.s caused by the streaming tearing instability in the earth's distant magnetotail has been studied numerically. The results show that after a brief phase of exponential growth, the growth rate of the streaming tearing instability is greatly reduced when the magnetic island width becomes comparable to the plasma sheet thickness and finally the magnetic island width saturates. The magnetic island width decreases as the magnetic Reynolds, number S increases, and it increases as the sheared flow thickness δv increases. In the case with S→∞ （η→0）, the streaming tearing mode retrogrades to the streaming sausage mode in which no magnetic reconnection occurs. When the spacecraft moves across the magnetic island caused by the streaming fearing instability, the north-then-south or south-then-north B_z signatures may be observed.