赤道面磁层顶位形的磁流体力学模拟研究  

An MHD simulation study on the location and shape of magnetopause in equatorial plane

作　　者：李传起[1,2] 顾斌[1] 母丽丽[1] 张青梅[1] 陈美红[1] 蒋勇[3] 

机构地区：[1]南京信息工程大学物理与光电工程学院,南京210044 [2]广西师范大学电子工程学院,桂林541004 [3]南京信息工程大学数学与统计学院,南京210044

出　　处：《物理学报》2012年第21期567-573,共7页Acta Physica Sinica

基　　金：国家自然科学基金(批准号:41174165;11105075)资助的课题~~

摘　　要：磁层顶位置和形状的动态特征描绘是地球物理和空间物理研究的难点之一.文章基于太阳风-磁层-电离层耦合的全球磁流体力学(MHD)数值模拟,运用电流密度极大法确定磁层顶位形,并具体研究两种典型太阳风动压(D_p)和几种不同行星际磁场的z分量(B_z)条件下,地球赤道面上方磁层顶动态特征.模拟结果显示,磁层顶日下点高度r_0主要由D_p控制.随着D_p增加,磁层顶被压缩,r_0显著减小.相同D_p条件下,在B_z由南向(B_z<0)逐渐减小,并转为北向(B_z>0)逐渐增大的过程中,r_0缓慢增大.不同条件下,磁层项张角φ变化较小,反映了赤道面磁层顶结构的相似性.与Shue98低纬磁层顶经验模型比较,MHD模拟能再现磁层顶日下点位置r_0对D_p的响应,而r_0随B_z变化的饱和性仅出现在低速太阳风条件下.MHD模拟和经验模型的磁层项张角φ差别小于2.5°,但模拟显示φ随B_z的变化趋势并非简单线性关系.The determination of the varying position and shape of magnetopause is one of the important Gordian knots in geophysics and space physics. According to the solar wind-magnetosphere-ionosphere coupling global magnetohydrodynamic （MHD） simulation, and with the maximum electric current criterion, we study the position and shape of the magnetopause under several solar wind dynamic pressure （Dp） and interplanetary magnetic field conditions. The simulation results show that the subsolar position （r0） of the magnetopause is controlled mainly by Dp with the significant decrease of r0 as Dp increases. At a certain Dp, when southword Bz （Bz〈0） decreases to zero, then shifts to northward （Bz〉0） and increases, the subsolar position r0 keeps increasing. For all cases studie here, the flare angle （φ） of the magnetopause experiences small changes. This provide an evidence for the structural self-similarity of magnetopause in equatorial plane. Compared with the empirical low-latitude magnetopause model of Shue98, MHD simulation can reproduce the dependence of the subsolar point r0 on Dp, while the saturation effect of r0 varying with Bz in empirical model is represented only with slow solar wind. As to the flare angle φ, although the difference between MHD simulation and empirical model is less than 2.5°, the variation of φ with Bz in MHD simulations is nonlinear and different from the linear trend in empirical model.

关 键 词：赤道面磁层顶 位置结构特征 磁流体力学模拟 

分 类 号：P353[天文地球—空间物理学]