Study of fast magnetic reconnection with multi-scale plasma magnet-hydrodynamic simulations

快速磁场重联是等离子体中的一种爆炸性能量转换机制，它将磁能转化为等离子体动能。最近的空间卫星观测表明，快速磁场重联被认为在太阳耀斑和地磁亚暴中起着至关重要的作用。等离子体物理学的主要困难在于，许多现象的机制是在极其广泛的时空范围内，即从电子的回旋运动到行星际空间，通过两种以上的基本机制的耦合来控制的。为了研究快速磁场重联过程，本文开发了多尺度等离子体模拟程序，并尝试通过数值模拟来验证Petschek型快速磁场重联模型的存在性。研究结果表明：1.在磁流体动力学理论研究的基础上，从快磁场重联区喷射出的等离子体团的传播速度是由磁流体动力学理论计算得到的 ...更多信息 由上游等离子体β值和等离子体团周围慢激波的张开角精确控制。2：基于MHD多尺度模拟程序，二维快磁重联在片电流方向的少量扰动下是不稳定的，并自发地发展为强局域化的三维快磁重联。并且，重连过程间歇地重复，并继续随机地喷射三维等离子体团。这一模拟结果似乎与TRACE卫星观测到的太阳耀斑中的等离子体下降流现象一致。3：还研究了MHD和粒子（动力学）模拟程序的组合。计算结果表明，该程序对于节省计算机内存，同时模拟磁中性点附近的电子-离子行为和磁流体动力学行为是非常有用的。但是，计算速度仍然不足以检查快速磁场重联的完整模拟。继续开发模拟代码。少

Fast magnetic reconnection is an explosive energy conversion mechanism in plasma, by which the magnetic energy is converted to the plasma kinetic energy. With recent space satellite observations, fast magnetic reconnection is considered to play a crucial role in solar flares and geomagnetic substorms. The major difficulty of the plasma physics is that the mechanisms of many phenomena are controlled through coupling of more than two basic mechanisms in an extremely wide range of space and time, i.e. from the gyration motion of electron to interplanetary space. In this study, in order to research the fast magnetic reconnection process, some multi-scale plasma simulation codes were developed and the existence of the Petschek type fast reconnection model was tried to be examined by the numerical simulations. The followings were revealed.1: On the basis of MHD (Magneto-hydrodynamic) theoretical study, the propagation speed of plasmoids ejected from the fast magnetic reconnection region is u … More niquely controlled by the upstream plasma beta value and the opening angle of the slow shock around the plasmoid.2: On the basis of MHD multi-scale simulation code, two-dimensional fast magnetic reconnection is unstable for a small amount of perturbations in the sheet-current direction and is spontaneously developed to three-dimensional fast magnetic reconnection which is strongly localized in the sheet current direction. And, the reconnection process is intermittently repeated and continues to randomly eject the three-dimensional plasmoids. This simulation result seems to be consistent with plasma downflowing phenomena in solar flares detected in TRACE satellite observations.3: The combination of the MHD and particle (kinetic) simulation codes was also studied. The code itself was constructed and it was revealed that the code is very useful to save the computer memory to simultaneously simulate the electron-ion behaviors at the magnetic neutral point and the MHD behaviors around there. But, the computational speed is still insufficient to examine the full simulation for the fast magnetic reconnection. The development of the simulation code is continued. Less