球坐标系六片网格下三维定态行星际太阳风模拟

采用二阶MacCormack差分格式, 利用稳态的磁流体(MHD)方程组在球坐标系六片网格下模拟研究了行星际太阳风. 六片网格系统能有效避免极区奇性和网格收敛性. 迭代按径向方向推进求解, 很大程度上减少了计算量, 节约了计算时间. 内边界条件根据太阳与行星际观测确定, 比较测试了5种内边界条件, 模拟给出了1922卡林顿周的背景太阳风结构. 几种内边界条件所得模拟结果与行星际观测基本吻合. 太阳风速度采用McGregor 等的经验公式给出, 磁场由水平电流片(HCCS)模型得到, 密度和温度分别根据动量守恒和气压守恒得到, 研究表明采用这样的边界条件模拟结果最佳. 

Three-dimensional Steady State Interplanetary Solar Wind Simulation in Spherical Coordinates with a Six-component Grid

In this paper, the MacCormack scheme is applied to the time-independent Magnetohydrodynamics (MHD) equations in spherical coordinates with a six-component grid for the three-dimensional interplanetary solar wind simulation. The use of six-component grid system can better body-fit the spherical shell domain of interplanetary space as well as avoid the singularity and the mesh convergence near the poles. The radial coordinate is treated as a time-like coordinate, thus can significantly reduce the computational time. The inner boundary distribution is determined by the empirical relations and observation. Five kinds of inner boundary conditions used formerly by MHD modelers are comparatively used to simulate the Carrington Rotation (CR) 1922 solar wind bac kground. The numerical results show that all these boundary conditions can produce consistent large-scale solar wind structure with the observation, and better result in agreement with observations can be achieved when adopting the following inner boundary condition: the radial speed is obtained by the empirical relationship proposed by McGregor et al. in 2011, the magnetic field is obtained by Horizontal Current Current Sheet (HCCS) model, an assumption of constant momentum flux is used to derive number density, and temperature is chosen to assure that the total pressure is uniform at the inner boundary.