Formation and Structure of Intermediate Shocks in Collisionless Plasmas

9224553卡里马巴迪在磁流体力学兰肯-胡格尼奥特关系式所允许的六种激波(快激波、慢激波和四种中间激波)中，对中间激波的了解最少。除了具有极大的理论意义外，中间激波的研究对于理解各种空间等离子体现象也是至关重要的，例如与日冕物质抛射有关的磁层顶和激波锋面。ISS在空间等离子体中提供了一个重要的耗散过程，是允许磁场旋转的仅有的两个等离子体不连续之一，另一个是旋转不连续(RD)。虽然ISS的存在最近已经在阻性MHD框架内得到证实，但对其在无碰撞等离子体中的性质知之甚少。这项工作是研究无碰撞等离子体中ISS的形成和性质及其与RDS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，将第一次被包括在计算中。我们将检验这一假设，即磁层顶和太阳风中的场旋转是由ISS而不是RDS引起的。我们将采取两种方法。一种是将ISS作为一个不受外部扰动的单一结构进行研究。另一种方法涉及形成多个不连续及其相互作用，很像在重新连接事件期间发生的那样。这项研究的目标是确定在什么条件下可以形成国际空间站，以及它们是否能够在存在扰动的情况下保持稳定。我们研究的主要工具是最先进的动力学数值模拟，尽管为了进行比较，也将进行MHD模拟。***

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. ***