黄道面内行星际激波相互碰撞作用过程研究——能量效应

MHD SIMULATION OF INTERACTIONS BETWEEN TWO NEIGHBORING INTERPLANETARY SHOCK WAVES——ENEGETIC EFFECTS

本文用两维半MHD数值模型,数值模拟研究了两邻近扰动源所产生的激波在行星际空间黄道面内不同能量时的相互碰撞过程。在内边界(18R_s)两扰动中心的间距取为36°。结果表明:两弱激波(速度在500km/s左右以下)不会产生汇合,而是各自独立地传播;两中等强度激波(速度在1000km/s左右)将发生汇合,但在IAU尚可分辨;两强激波(速度在2000km/s以上)则在1AU以内已发生汇合,汇合后形成一个新激波,其磁场结构与单激波明显不同。激波能量越大,两激波汇合的越快。

A MHD 2 1/2D,time-dependent model is used to investigate a series,individually of neighboring interplanetary shock wave interactions in the equatorial plane.For an azimuthal angular separation of 36 degree,between the centers of two disturbances,four different initial velocities,vs=500,1000 2000 and 3000 km/s are considered in this paper.The results indicate: for the case of vs=2000 and 3000 km/s,the two shock waves have already coalesced into a new shock within 1 AU,there are not any two peaks in the velocity,desity and temperature.From those parameters at 1 AU,it is difficult to identify whether this new shock wave coalesced from two shock waves,however,the magnetic field distribution in the new shock is very distinct from a single shock wave;for the case of vs=1000 km/s,the two shock waves have not completely coalesced into a new shock wave,and the peak of shock parameters of each shock wave can be identified from their distributions;for the case of vs=500 km/s,the coalescence would almost not occur,in fact,the two shock waves would decayed independently into ordinary MHD waves near 0.3 AU.