多层电流片中撕裂模不稳定性的数值研究

NUMERICAL STUDIES OF TEARING MODE INSTABILITY IN A MULTIPLE CURRENT SHEET

应用二维磁流体动力学模拟方法数值研究了三层电流片中电阻撕裂模不稳定性的特征及磁场重联过程．结果表明，这是一种复杂的非稳态磁场重联．在初期阶段，三个电流片中分别由撕裂模不稳定性引起磁场重联，形成薄而长的磁岛．随着撕裂模不稳定性的非线性发展，每个磁岛的宽度都逐步增大，以至导致新的磁场重联发生．同时，三个电流片的强度都逐渐减弱，且原中心反向电流区最终消失．部分磁能不断地转化为等离子体的热能和动能，引起等离子体的加热和加速．多层电流片中撕裂模不稳定性引起的自发重联，可能对太阳耀斑、日冕加热、太阳风与磁层耦合等有重要影响．

The charadristics of resstance tearing instability and the promp of magnetic amnnedon in a three-layer current sheet are studied numerically by two-dimensional magnetohydrodyndric simulation. The results show that it is a complex unsteady magnetic reconnection. In the early stage, magneti reconnections are caused by the tearing mode instability in three current respectively, and the thin and long magnetic islands are formed. Accompanying to the nonlinear deveopment of tearing mode instability, the width of eadi magnetic island increases with time, and it leads new magnetic amImection. At the same time, the current intensity in three current sheets decreases gndualy and the reverse curren in the central region disappears finally. A ponion of magnetic energy converts into thennal energy and kineti energy, and leads plasma heating and acceleration The spontaneous amnnection caused by tearing mode instability in the mulple currend sheet may be important for solar flare, corona heating and the coupling between the solar wind and the rnagnetosnhere.