Formation and Structure of Intermediate Shocks in Collisionless Plasmas

[224553] Karimabadi在磁流体动力学（MHD）朗肯-休戈尼奥特关系允许的六种激波（快速、慢速和四种中间激波）中，中间激波是最不容易理解的。除了具有重要的理论意义外，中间激波（ISs）的研究对于理解各种空间等离子体现象至关重要，例如与日冕物质抛射相关的磁层顶和激波锋。国际空间站在空间等离子体中提供了一个重要的耗散过程，是仅有的两个允许磁场旋转的等离子体不连续之一，另一个是旋转不连续（RD）。虽然国际空间站的存在最近已经在电阻MHD框架内建立起来，但对它们在无碰撞等离子体中的特性知之甚少。本研究旨在探讨无碰撞等离子体中ISs的形成和性质及其与rd的关系，并将其应用于空间等离子体。许多重要的影响，如温度各向异性，将首次被包括在计算中。我们将检验磁层顶和太阳风中的磁场旋转是由于ISs而不是rd的假设。将采取两种方法。一个是将国际空间站作为一个不受外部扰动的单一结构进行研究。另一种方法涉及多个不连续的形成及其相互作用，就像在重新连接事件中发生的那样。这项研究的目的是确定国际空间站形成的条件，以及它们是否能在扰动存在的情况下保持稳定。我们研究的主要工具是最先进的动力学数值模拟，尽管为了比较，MHD模拟也将进行。＊＊＊

9224553 Karimabadi Of the six types of shocks (fast, slow, and four types of intermediate shocks) allowed by magnetohydrodynamic (MHD) Rankine- Hugoniot relations, intermediate shocks are the least understood. Besides being of great theoretical interest, the study of intermediate shocks (ISs) is essential to the understanding of diverse space plasma phenomena, such as the magnetopause and shock fronts associated with coronal mass ejections. ISs provide an important dissipation process in space plasmas and are one of only two plasma discontinuities that allow for the rotation of the magnetic field, with the other being the rotational discontinuity (RD). Although the existence of ISs has recently been established within the resistive MHD framework, far less is known about their properties in collisionless plasmas. This work is to investigate the formation and properties of ISs and their relation to RDs in collisionless plasmas with applications to space plasmas. For the first time many important effects, such as temperature anisotropy, will be included in the calculations. We will examine the hypothesis that field rotations at the magnetopause and in the solar wind are due to ISs rather than RDs. Two approaches will be taken. One is the study of ISs as a single structure removed from external perturbations. The other approach involves the formation of multiple discontinuities and their interactions, much as would occur during reconnection events. The goal of this study is to determine the conditions under which ISs can be formed, and whether they can remain stable in the presence of perturbations. The primary tools of our investigation are state-of-the-art kinetic numerical simulations, although for comparison, MHD simulations will also be performed. ***