磁化天体物理等离子体中浮力不稳定性的多分量理论：MHD分析的再讨论
Multicomponent theory of buoyancy instabilities in magnetized astrophysical plasmas: MHD analysis revisited
摘要：
本文不是基于MHD方程，而是采用多组分等离子体方法，发展了一种电子-离子等离子体的浮力不稳定性理论。我们研究的几何背景磁场，重力和分层是沿一个轴。没有简化通常的MHD方法在研究这些不稳定性。包括背景电子热通量和电子与离子之间的碰撞。我们推导出简单的色散关系，这表明，热通量扰动一般稳定的不稳定性。存在温度梯度的狭窄区域，其中可能存在不稳定性。这一结果与MHD方法中得到的结论相矛盾。我们表明，这种矛盾的原因是简化的假设中使用的MHD分析的浮力不稳定性和纵向电场扰动的作用，这是没有捕获的MHD方程。我们的色散关系还表明，如果离子和电子的温度梯度具有相反的符号，则具有电子热通量的介质可以是不稳定的。所得结果可应用于ICM和星系团。
英文摘要：
We develop a theory of buoyancy instabilities of the electron-ion plasma with the heat flux based on not the MHD equations, but using the multicomponent plasma approach. We investigate a geometry in which the background magnetic field, gravity, and stratification are directed along one axis. No simplifications usual for the MHD-approach in studying these instabilities are used. The background electron thermal flux and collisions between electrons and ions are included. We derive the simple dispersion relation, which shows that the thermal flux perturbation generally stabilizes an instability. There is a narrow region of the temperature gradient, where an instability is possible. This result contradicts to a conclusion obtained in the MHD-approach. We show that the reason of this contradiction is the simplified assumptions used in the MHD analysis of buoyancy instabilities and the role of the longitudinal electric field perturbation, which is not captured by the MHD equations. Our dispersion relation also shows that a medium with the electron thermal flux can be unstable, if the temperature gradient of ions and electrons have the opposite signs. The results obtained can be applied to ICM and clusters of galaxies.
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