电场驱动的日冕数值模拟中时变边界条件研究

Time-dependent boundary conditions for electric-field-driven global coronal simulations

时变边界条件的处理对于数据驱动的日冕太阳风建模研究十分重要.本文基于特征边界条件,将松弛型无反射边界处理应用到三维磁流体力学(Magnetohydrodynamics,MHD)方程中,发展出一种自洽的、以切向电场作为数据驱动的时变边界条件,并将其应用于时变日冕太阳风的模拟中.为验证该时变边界条件的有效性,本文连续模拟研究了2187—2189三个卡林顿周的日冕太阳风结构.通过将模拟结果与SOHO、STEREO等卫星的观测结果进行对比研究,发现基于该时变边界条件的日冕太阳风的模拟可以较好地反映出日冕太阳风的大尺度结构及其演化过程,且模拟得到的太阳风参数与卫星观测结果较为吻合.说明本文所发展的时变边界条件可以有效地模拟数据驱动的时变日冕太阳风.

The treatment of time-dependent boundary conditions is of great importance for data-driven magnetohydrodynamics(MHD)modeling of the global solar corona and the solar wind.In this paper,the relaxation-type nonreflecting boundary is applied to the 3D MHD equations based on the characteristic boundary conditions(CBC),and a self-consistent time-dependent boundary condition with the tangential electric field as the driving data is developed.This boundary condition is further applied to the time-dependent solar corona simulation.In order to verify the validity of this boundary condition,we simulate the solar corona structure of three Carrington rotations(CRs)2187-2189 consecutively.Comparing the simulated results with the observed results of SOHO,STEREO and other satellites,we found that the simulation of the solar corona and the solar wind based on the time-dependent boundary conditions can better reflect the large-scale structure of the solar corona and its evolution process,and the simulated parameters are in good agreement with the observations.It shows that the time-dependent boundary conditions developed in this paper can effectively simulate the time-dependent solar corona and the solar wind.