MHD模拟磁尾横断面结构与太阳风粒子注入机制

基于全球三维磁层MHD（Magnetohydrodynamics）模拟模型， 研究了行星际磁场（Interplanetary Magnetic Field， IMF）北向与南向时磁尾横断面（X=?18 R_E）的结构及等离子片的粒子注入机制. 模拟结果很好地符合一些已知的观测数据和经验模型. 从向阳面磁层顶IMF及重联后磁力线尾向运动过程的角度， 对磁尾横断面粒子热压力分布、磁力线投影、等离子片或电流片旋转、粒子流场分布等结构进行了合理的解释. 根据模拟得到的磁尾横断面结构， 及IMF北向与南向时磁力线投影显著不同的位形， 可以通过E×B漂移很好地说明不同IMF条件下， 太阳风粒子对磁尾等离子片的不同注入特性. 另外， 还通过磁尾横断面磁场梯度的计算， 说明了太阳风向等离子片粒子注入的晨-昏不对称性.

Simulation of the cross sections of the magnetotail and particle transferred into the plasma sheet under north- and southward IMF conditions

By a newly modified global MHD simulation model, We have studied the structure of the cross sections of the magnetotail (X=?18 R_E) and the mechanism of plasma transferred into plasma sheet under different IMF conditions(north- and southward). The results are consistent with some observations and experiential models. We illustrate the properties of thermal pressure, magnetic field projection, plasma or current sheet rotation, and flow field at the X=?18 R_E cross section, and explain the features by the tailward-moving processes of IMF and reconnected field lines on the dayside magnetopause. We find the magnetic field projections on the tail cross section have different configurations under different IMF conditions, and the differences can easily reveal the nature of plasma ejected into the plasma sheet from solar wind by E×B mechanism. Furthermore, we have calculated the magnetic grid-drift distributions at the tail cross section, and point out the possible reason of the dawn-dusk asymmetry of solar wind particles transferring into the plasma sheet.