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

多尺度等离子体磁体流体动力学模拟的快速磁重联研究

基本信息

批准号：
15540475
负责人：
SHIMIZU Tohru
金额：
$ 2.3万
依托单位：
Ehime University
依托单位国家：
日本
项目类别：
Grant-in-Aid for Scientific Research (C)
财政年份：
2003
资助国家：
日本
起止时间：
2003 至 2006
项目状态：
已结题

项目摘要

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

快速磁重联是等离子体中的一种爆炸能量转换机制，通过它将磁能转化为等离子体动能。根据最近的空间卫星观测，快速磁重联被认为在太阳耀斑和地磁亚暴中发挥着关键作用。等离子体物理学的主要困难在于，许多现象的机制是由两个以上的基本机制在极大的时空范围内耦合控制的，即从电子的回转运动到行星际空间。为了研究快速磁重联过程，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型快速重联模型的存在性。研究结果表明：1.在磁流体理论研究的基础上，得到快磁重联区中等离子体粒子的传播速度为u…。2.在MHD多尺度模拟程序的基础上，二维快速磁重联对于片流方向的少量扰动是不稳定的，而自发发展为三维快速磁重联，它在片流方向上是强烈局域化的。并且，重新连接过程被间歇地重复，并继续随机地弹出三维等离子体体。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流现象相一致。3：还研究了MHD和粒子(动力学)模拟程序的结合。对程序本身进行了构造，结果表明，该程序对节省计算机内存，同时模拟磁中性点的电子-离子行为和磁中性点附近的MHD行为非常有用。但是，计算速度仍然不足以检验快速磁重联的完整模拟。仿真代码的开发还在继续。较少