磁化等离子体中浮力不稳定性的多分量理论：平行于重力的磁场的情况
Multicomponent theory of buoyancy instabilities in magnetized plasmas: The case of magnetic field parallel to gravity
摘要：
我们研究了电子-离子等离子体的电磁浮力不稳定性与热通量的基础上，而不是磁流体动力学（MHD）方程，但使用多组分等离子体方法时，解决每个物种的动量方程。我们考虑一个几何形状，其中背景磁场，重力和分层是沿一个轴。考虑了非零背景电子热通量。电子和离子之间的碰撞包含在动量方程中。没有简化通常的单流体MHD方法在研究这些不稳定性。我们推导出一个简单的色散关系，这表明，热通量扰动一般稳定的不稳定性的几何考虑。这一结果与磁流体动力学方法的结论相矛盾。我们表明，这种矛盾的原因是简化的假设中使用的浮力不稳定性的MHD分析和纵向电场扰动的作用，这是不捕获的理想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。所得结果可应用于实验室和天体物理中的弱碰撞磁化等离子体物体。
英文摘要：
We investigate electromagnetic buoyancy instabilities of the electron-ion plasma with the heat flux based on not the magnetohydrodynamic (MHD) equations, but using the multicomponent plasma approach when the momentum equations are solved for each species. We consider a geometry in which the background magnetic field, gravity, and stratification are directed along one axis. The nonzero background electron thermal flux is taken into account. Collisions between electrons and ions are included in the momentum equations. No simplifications usual for the one-fluid MHD-approach in studying these instabilities are used. We derive a simple dispersion relation, which shows that the thermal flux perturbation generally stabilizes an instability for the geometry under consideration. This result contradicts to 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 ideal MHD equations. Our dispersion relation also shows that the medium with the electron thermal flux can be unstable, if the temperature gradients of ions and electrons have the opposite signs. The results obtained can be applied to the weakly collisional magnetized plasma objects in laboratory and astrophysics.
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