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Three Dimensional Modeling and Computer Simulations of fast magnetic Reconnection

快速磁重联的三维建模和计算机模拟

基本信息

批准号：
05455016
负责人：
UGAI Masayuki
金额：
$ 4.67万
依托单位：
Ehime University
依托单位国家：
日本
项目类别：
Grant-in-Aid for General Scientific Research (B)
财政年份：
1993
资助国家：
日本
起止时间：
1993 至 1995
项目状态：
已结题

项目摘要

The main theme of the present research has been directed to studying the basic physical mechanism of large dissipative events, such as solar flares and geomagnetic substorms. It is well understood that the fast reconnection mechanism, involving slow shocks, is quite applicable to flare phenomena. Then, a very essential question is how the fast reconnection mechanism can develop and be established as an eventual solution in actual space plasmas? Historically, two theoretical models have been proposed with respect to this question. One is the so-called externally driven fast reconnection model. In this model, external boundary conditions determine the basic configuration, whereas a finite resistivity plays no important role on the fast reconnection evolution. On the other hand, we have proposed the so-called spontaneous fast reconnection model. In this model, the fast reconnection develops because of the self-consistent interaction between (microscopic) localized anomalous resistivities and (macroscopic) reconnection flows. By a number of computer simulations, we have demonstrated that the spontaneous fast reconnection model should be most applicable to space plasmas. On the basis of the spontaneous fast reconnection model, we have obtained the following fundamental results in the presence of (three-dimensional) sheared fields. (1) The associated magnetic energy conversion can be effectively performed by the large-scale motor effects in the slow-shock layrs. (2) The formation and propagation of a large-scale plasmoid is the direct outcome of the spontaneous fast reconnection mechanism. (3) Even in fully three-dimensional situations, the spontaneous fast reconnection model is available if the initial current sheet is sufficiently large.

当前研究的主题是研究太阳耀斑和地磁亚暴等大型耗散事件的基本物理机制。众所周知，包含慢激波的快速重联机制对耀斑现象是相当适用的。那么，一个非常关键的问题是如何在实际空间等离子体中发展和建立快速重联机制作为最终的解决方案？历史上，关于这个问题提出了两种理论模型。一种是所谓的外部驱动快速重联模型。在这个模型中，外部边界条件决定了基本的配置，而有限的电阻率起不了重要的作用的快速重联演变。另一方面，我们提出了所谓的自发快速重联模型。在这个模型中，快速重联的发展，因为自洽的相互作用（微观）局域反常的折射率和（宏观）重联流。通过大量的计算机模拟，我们证明了自发快速重联模型对空间等离子体的适用性。在自发快速重联模型的基础上，我们在（三维）剪切场存在下得到了下列基本结果。(1)慢激波层中的大尺度电动机效应可以有效地进行相关的磁能转换。(2)大尺度等离子体团的形成和传播是自发快速重联机制的直接结果。(3)即使在完全三维的情况下，自发快速重联模型是可用的，如果初始电流片足够大。