无碰撞激波的理想MHD模拟

SIMULATION OF SPACE COLLISIONLESS SHOCK WITH IDEAL MHD EQUATIONS

采用了WENO格式数值求解一维理想MHD方程组,模拟了行星际无碰撞激波,研究了垂直无碰撞激波与行星际反向磁场结构和高密度等离子体团的相互作用过程,并与粒子模拟的结果进行比对,两者的结果非常类似.模拟结果表明,对涉及无碰撞激波的大部分现象中理想MHD模拟是准确且可行的,同时相对于粒子模拟又有很好的计算效率,便于扩展至二维或三维的情形.

The collisionless shocks are the common phenomena in the interplanetary and interstellar space. They are also the important fundamental subject in the research of plasma physics, space physics and astrophysics. Numerical simulation is widely used in the study of collisionless shocks. Corresponding to the particle simulation, the method of solving the ideal MHD equations with WENO scheme has been presented to simulate the space collisionless shock. Based on the method, the interaction between the quasi-perpendicular collisionless shocks and two kinds of interplanetary structure——C inversed magnetic field and plasmoid with high density has been studied, and the results have also been compared with those of particle simulation, to consider the feasibility and the accuracy of MHD method in the simulation of collisionless shock. The comparison between the results of two method shows that, the MHD simulation can provide most results that are observed in the particle simulation, thus it is feasible to simulate the quasi-perpendicular collisionless shock with MHD method when the dynamic effects can be omitted. It also has a higher computational efficiency than the particle simulation, and will be easier to extend to the 2D or 3D simulation. However, the MHD simulation does not include the effect caused by single particle. So it lacks the capacity to describe the dynamic effects such as the dissipation and detailed structure of collisionless shocks. If the phenomena caused by these effects are not so important in specific research topics, the MHD simulation still can provide satisfied results. In some other cases, MHD simulation can be a convenient way to forecast the behavior of large-scale particle simulation.