各向异性热传导条件下Rayleigh-Taylor稳定和不稳定接触间断的动力学
The Dynamics of Rayleigh-Taylor Stable and Unstable Contact Discontinuities with Anisotropic Thermal Conduction
摘要：
研究了弱碰撞等离子体中沿磁场线的各向异性热传导对加速接触不连续性的影响。我们首先进行线性稳定性分析类似于用于推导瑞利-泰勒不稳定性（RTI）色散关系。我们发现，各向异性传导是唯一重要的可压缩模式，不可压缩模式是等温的。在各向异性传导的存在下，模式增长得更快，但增长率的变化不会超过一个因素的顺序统一。接下来，我们运行完全非线性数值模拟的接触不连续性与各向异性传导。非线性演化可以被认为是三种物理效应的叠加：由于垂直传导引起的温度扩散、RTI和热通量驱动的浮力不稳定性（HBI）。在具有RTI稳定接触不连续性的模拟中，温度不连续性由于垂直热传导而扩散。由于初始垂直速度扰动和跨界面的数值混合，即使对于初始水平磁场也会发生这种情况。HBI通过将最初垂直的磁场线重新定向为更水平的几何形状来减缓这种温度扩散。在具有RTI不稳定接触不连续性的模拟中，动力学最初由温度扩散控制，但RTI在后期变得越来越重要。我们讨论了这些结果的可能应用超新星遗迹，太阳辐射，和冷锋在星系团。
英文摘要：
We study the effects of anisotropic thermal conduction along magnetic field lines on an accelerated contact discontinuity in a weakly collisional plasma. We first perform a linear stability analysis similar to that used to derive the Rayleigh-Taylor instability (RTI) dispersion relation. We find that anisotropic conduction is only important for compressible modes, as incompressible modes are isothermal. Modes grow faster in the presence of anisotropic conduction, but growth rates do not change by more than a factor of order unity. We next run fully non-linear numerical simulations of a contact discontinuity with anisotropic conduction. The non-linear evolution can be thought of as a superposition of three physical effects: temperature diffusion due to vertical conduction, the RTI, and the heat flux driven buoyancy instability (HBI). In simulations with RTI-stable contact discontinuities, the temperature discontinuity spreads due to vertical heat conduction. This occurs even for initially horizontal magnetic fields due to the initial vertical velocity perturbation and numerical mixing across the interface. The HBI slows this temperature diffusion by reorienting initially vertical magnetic field lines to a more horizontal geometry. In simulations with RTI-unstable contact discontinuities, the dynamics are initially governed by temperature diffusion, but the RTI becomes increasingly important at late times. We discuss the possible application of these results to supernova remnants, solar prominences, and cold fronts in galaxy clusters.
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