在热等离子体中模拟冷气体云时的物理学见解
Insights into the physics when modeling cold gas clouds in a hot plasma
摘要：
本文旨在研究一些经常提出的，但没有得到证实的参数嵌入或移动通过热等离子体的冷气体云的建模的可靠性，并在敏化建模者更仔细地考虑不可避免的代理物理过程及其相关性。首先，通过数值模拟，我们证明了星际云的自引力的影响越来越大，而且，通过这一点，反对他们的初始设置均匀。我们应用自适应网格细化代码{ \sc Flash}扩展到金属依赖的辐射冷却和外部加热的气体，自引力，质量扩散，和半解析的分子解离和原子电离。我们表明，金斯质量或Bonnor-Ebert质量的标准，分别只提供了一个充分的，但不是一个必要的条件，自引力是有效的，因为即使是低质量的云影响合理的动力学时间尺度。本文的第二部分致力于分析研究减少热传导的磁偶极子field.We表明，在这种配置，有效的热流，即在云表面上集成，抑制只有$32$百分之磁场的能量均分和仍然不显着，即使是更高的磁场强度。
英文摘要：
This paper aims at studying the reliability of a few frequently raised but not proven arguments for the modeling of cold gas clouds embedded in or moving through a hot plasma and at sensitizing modelers to a more careful consideration of unavoidable acting physical processes and their relevance. At first, by numerical simulations we demonstrate the growing effect of self-gravity on interstellar clouds and, by this, moreover argue against their initial setup as homogeneous. We apply the adaptive-mesh refinement code {\sc Flash} with extensions to metal-dependent radiative cooling and external heating of the gas, self-gravity, mass diffusion, and semi-analytic dissociation of molecules and ionization of atoms. We show that the criterion of Jeans mass or Bonnor-Ebert mass, respectively, provides only a sufficient but not a necessary condition for self-gravity to be effective, because even low-mass clouds are affected on reasonable dynamical timescales. The second part of this paper is dedicated to analytically study the reduction of heat conduction by a magnetic dipole field.We demonstrate that in this configuration, the effective heat flow, i.e. integrated over the cloud surface, is suppressed by only $32$ per cent by magnetic fields in energy equipartition and still insignificantly for even higher field strengths.
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