Computer Simulations of Electrodynamical Energy Conversion by Magnetic Reconnection

复杂空间等离子体现象的理论研究已通过计算机模拟完成。超级计算机的最新进展在很大程度上促进了许多实际和重要问题的处理。目前的项目集中于以下两个主要主题。(1)提出了有效处理磁流体动力学方程的适当算法，并通过实际数值计算验证了算法的有效性。算法主要针对数值边界条件、数值误差校验等方面进行了设计。特别是，为了在合理的CPU时间内进行三维MHD模拟，开发了与超级计算相关的算法。(2)在此基础上，进行二维MHD模拟，研究空间等离子体物理研究热点之一——耀斑等灾难性事件发生的基本物理机制。然后，我们提出了一个原始的物理模型，表明耀斑的快速磁能转换可以通过自发的快速重联发展来实现。特别是，已经证明了由快速重联产生的超音速等离子体射流与大尺度磁环碰撞并在界面处产生强烈的快速激波，从而使等离子体沿磁环加热非常有效。我们现在继续开发与超级计算机相关的3D MHD模拟代码，并且我们正在进行具有足够精确计算的3D模拟。

Theoretical studies of complicated space plasma phenomena has been done by computer simulations. Recent advance of supercomputers has largely facilitated the processing of many practical and important problems. The present project has been focused on the following two major subjects.(1) Appropriate algorithms for the effective processing of magnetohydrodynamic equations have been developed, and their validity has been examined by actually performing numerical computations. The algorithms have mainly been designed for numerical boundary conditions, numerical error check, etc.. In particular, algorithms relevant for supercomputing has been developed in rder to carry out three-dimensional MHD simulations within reasonable CPU time.(2) Next, on the basis of the algorithms developed, 2D MHD simulations have been done in order to study the basic physical mechanism involved in catastrophic events like flares, which has been one of the main topics in space plasma physics. We have then suggested an original physical model that states that rapid magnetic energy conversion responsible for flares can be realized by the spontaneous fast reconnection development. In particular, it has been demonstrated that a supersonic plasma jet, resulting from the fast reconnection, collides with a large-scale magnetic loop and causes a strong fast shock at the interface, which enables quite effective plasma heating along the loop.We now continue to develop the code of 3D MHD simulations relevant for supercomputers, and we are doing a 3D simulation with sufficiently precise computation.