引力场中磁场重联的数值研究（Ⅲ）等离子体团的形成和运动

应用解析和数值相结合的方法求得了含有闭场区、中性片和开场区的二维局域磁静力平衡日冕基态，进而在此基态下数值研究了由电阻撕裂模不稳定性引起的磁场重联过程．结果表明，在电流片长度远大于其半宽度的情况下，仍将发生具有两个Ｘ线的磁场重联，形成磁岛和高温高密度的等离子体团．等离子体团运动的方向取决于闭合区底部等离子体压力和磁压的比值β_０．当β_０较大时，等离子体团向下运动，引起结合不稳定性和磁岛的合并，等离子体团中的等离子体不断落入闭合磁场区两侧．当β_０较小时，等离子体团向上运动，导致电流片中等离子体的喷发．结果还表明，磁张力的分布是决定等离子体团运动方向的主要因子．

NUMERICAL STUDIES FOR MAGNETIC RECONNECTION IN A GRAVITATIONAL FIELD（Ⅲ）FORMATION AND MOTION OF THE PLASMOIDS

By using a combined method with analytical and numerical methods,two-dimensional basic states which consisting of the closed region, the neutral sheet and the open region,for the solar corona with local magnetostatic equilibrium are obtained.Magnetic reconnection caused by resistance tearing instability under this basic state has been studied numerically.The results show that magnetic reconnection with two X lines occured and the magnetic island and plasmoid with high temperature and high density formed when the length of the current sheet is much larger than its half-width.The moving direction of plasmoid depends on the ratio β_０ of plas ma and magnetic pressures at the bottom of closed region.When β_０ is larger,the plasmoid moves downwards.It leads to the coalescence instability and the merging of magnetic island.The plasmas in the plasmoid falls gradually into two sides ofthe closed region.When β_０ is smaller,the plasmoid moves upwards.It leads to upward ejection of plasma in the region of current sheet.The results also show that the distribution of magnetic tensor is a principal factor deciding the moving direction of plasmoid.