IMF北向与南向时地球磁尾等离子片粒子注入机制  

Simulation and comparison of particles entering the plasma sheet under northward and southward IMF conditions

作　　者：郭九苓[1,2] 沈超[2] 刘振兴[2] 

机构地区：[1]北京大学现代教育技术中心,北京100871 [2]中国科学院空间科学与应用研究中心,空间天气学国家重点实验室,北京100080

出　　处：《科学通报》2012年第34期3295-3300,共6页Chinese Science Bulletin

基　　金：国家自然科学基金(40731054;40974101);国家重点基础研究发展计划(2011CB811404)资助

摘　　要：基于自己开发的全球三维磁层MHD模拟模型及试验粒子方法,研究了行星际磁场(Interplanetary Magnetic Field,IMF)北向与南向时磁尾等离子片的粒子注入机制.结果发现,IMF北向与南向时太阳风粒子都可以穿越磁层顶进入近磁尾等离子片.IMF北向时太阳风粒子注入等离子片主要通过磁尾晨昏侧低纬度边界区,平均能量为几百电子伏特;而IMF南向时粒子则主要由南北两侧进入等离子片,平均能量则增至几千电子伏特.IMF南向比北向时磁尾张开更大的角度,这会使近地较高能量的粒子更容易沿磁力线进入磁尾及等离子片.结果定性地说明和解释了某些重要的观测事实:磁尾等离子片粒子在IMF北向时主要来源于太阳风,而南向时则主要来源于地球.Using a newly modified global magnetohydrodynamics （MHD） simulation model and test-particle method, we investigated the mechanism of plasma transfer into the near-tail plasma sheet under different interplanetary magnetic field （IMF） conditions （northward and southward）. The results explain some well-known observations and clearly reveal the physical nature of the plasma transfer： particles mainly originate from the solar wind under a northward IMF and from the Earth under a southward IMF. We found solar wind particles transfer into the plasma sheet through dusk and dawn flanks under a northward IMF, and the transfer paths are consistent with merging sites on the magnetopause. When the IMF is southward, the solar-wind plasma transferring into the plasma sheet is mainly from the northem and southern sides. The average energy of the injected ions is much higher when the IMF is southward, which would result in a shorter stay-time in the plasma sheet. The tail terrestrial magnetic field lines are more open in the north-south direction when the IMF is southward, and this pattern makes it easier for terrestrial particles with higher energies to be ejected into the plasma sheet.

关 键 词：等离子片 试验粒子 MHD 模拟 太阳风 IMF 南北向 

分 类 号：P353[天文地球—空间物理学]