Simulation of collisionless plasma with the Vlasov method
Simulation of collisionless plasma with the Vlasov method
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发表时间：
2012
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通讯作者：
T. Umeda
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作者：
T. Umeda
空间等离子体是一种无碰撞、多尺度、高度非线性的介质。有许多类型的自洽计算机模拟，根据各种近似处理空间等离子体。全球尺度动力学通常由磁流体动力学（MHD）、Hall-MHD和多流体模型描述，而电子尺度过程由动力学模型描述，即，麦克斯韦方程和带电粒子的牛顿-洛伦兹方程或弗拉索夫（无碰撞玻尔兹曼）方程。混合方法将离子视为粒子，将电子视为离子尺度过程的流体。传统上，MHD模拟已被用于全球规模的问题，如恒星和行星的磁层的数值模拟。然而，MHD模拟需要扩散系数，这基本上是由于在MHD近似的框架中被消除的动力学过程。最近的高分辨率原位观测也表明，空间等离子体中的流体尺度和动力学尺度之间存在着强耦合，即跨尺度耦合。为了理解空间等离子体中的跨尺度耦合，重要的是在全球尺度模拟中包括完整的动力学，这是本研究的目标。
Space plasma is a collisionless, multi-scale, and highly nonlinear medium. There are numerous types of selfconsistent computer simulations that treat space plasma according to various approximations. The global-scale dynamics are commonly described by magneto-hydrodynamic (MHD), Hall-MHD and multi-fluid models, while electron-scale processes are described by the kinetic model, i.e., the Maxwell equations and either the Newton-Lorentz equation for charged particles or the Vlasov (collisionless Boltzmann) equation. Hybrid methods treat ions as particles and electrons as a fluid for ion-scale processes. Conventionally, MHD simulations have been used for numerical modeling of global-scale problems such as magnetospheres of stars and planets. However, the MHD simulations need diffusion coefficients, which are essentially due to kinetic processes that are eliminated in the framework of the MHD approximation. Recent high-resolution in-situ observations have also suggested that fluid scale and kinetic scale in space plasma are strongly coupled with each other, which is called cross-scale coupling. To understand the cross-scale coupling in space plasma, it is important to include full kinetics in global-scale simulations, which is the goal of this study.