1998年5月日冕三维结构的数值模拟  

THREE-DIMENSIONAL NUMERICAL CORONAL MODEL OF CARRINGTON ROTATION 1935 AT MAY 1998

作　　者：叶占银[1] 魏奉思[1] 冯学尚[1] 石勇[1] 姚久胜[1] 

机构地区：[1]中国科学院空间科学与应用研究中心,北京100080

出　　处：《空间科学学报》2001年第4期289-296,共8页Chinese Journal of Space Science

基　　金：中国科学院空间科学与应用研究中心所长基金资助(992002)

摘　　要：采用三维理想磁流体力学（ＭＨＤ）模式，内边界条件把二维投影特征线边界方法推广应用到三维计算，有效地稳定了数值计算并保证稳态解的自洽性；初始猜解磁场由１９３５卡林顿周光球磁场观测数据得到，这样计算得到的１９９８年５月份期间日冕三维结构比较符合实际．计算结果表明：（１）计算得到的源表面非径向磁场量值在磁中性线附近不超过２μＴ，表明源表面磁场基本径向．（２）模拟得到的源表面径向磁场量值除了在磁中性线附近的区域外变化不大，这和观测一致．（３）由源表面磁场按平方反比的规律计算出 １ ＡＵ处磁场量值更接近观测值．（４）计算得到的日冕结构和观测定性一致．三维数值模拟结果还表明，日冕的三维大尺度背景结构主要是由磁场决定的，在闭磁场处或者电流片附近，太阳风的密度高，速度低；在开场区，太阳风的密度低，速度高．Three-dimensional coronal structure of Carrington rotation 1935 at May 1998 is obtained by using a three-dimensional numerical model of ideal magnetohydro dynamic equations. In this numerical model, MacCormark-Ⅱ scheme is employed for the discretization of the governing equations in computational domain and non- reflecting projected-characteristic condition is adopted at inner boundary to keep the simulation stable and the solution self-consistent. With the numerical model, iteration is carried out with initial magnetic field constructed from photosphere observation at 1935 Carrington rotation by Legendre series expansion and finally approaches a steady state. The iteration results show that: (1) magnetic field on source surface is nearly in radial direction with non-radial magnetic field compo-nent no more than 2μT near the neutral line. (2) The value of radial magnetic field component on source surface has no much variation except near the neutral line. This agrees with Ulysess observation. (3) The magnitude of radial magnetic field component at 1 AU, calculated from that on source surface by rule of r-2, approxi mates observation better than that obtained by potential model. (4) 3-D numerical coronal structure agrees qualitatively with observation. The 3-D numerical results also show that magnetic field dominates global solar wind structure, in which den- sity of solar wind is high and speed is low in close magnetic field and near current sheet, while density is low and speed is high at open magnetic field.

关 键 词：三维理想磁流体力模式 MHD数值模拟 日冕三维结构 日地空间太阳风 

分 类 号：P182.62[天文地球—天文学] O242[理学—计算数学]