Computer Simulations of Electrodynamical Energy Conversion by Magnetic Reconnection

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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.