电子和离子能量交换对磁化天体长波热不稳定性的影响
Influence of energy exchange of electrons and ions on the long-wavelength thermal instability in magnetized astrophysical objects
摘要：
我们研究了与星系团、日冕和其他双组分天体有关的电子-离子磁化等离子体的热不稳定性。我们应用多组分等离子体的方法时，所有的物种的动力学被认为是单独通过电场扰动。本文中得到的扰动的一般表达式可以适用于广泛的多组分天体物理和实验室等离子体也包含中性粒子，尘埃颗粒，和其他物种。我们假设电子和离子的背景温度是不同的，并在热方程中包含能量交换。我们考虑到碰撞频率对密度和温度扰动的依赖性。电子和离子的冷却-加热函数是不同的。作为一个具体的情况下，我们考虑的凝聚模式的热不稳定性的长波长扰动时的动力学时间小于的时间，在此期间，由于热速度的粒子覆盖沿磁场的波长。我们推导出一个一般的色散关系，考虑到上述影响，并获得简单的表达式的增长率在极限情况下。扰动被证明具有电磁性质。我们发现，在所考虑的条件下，横向尺度大小的不稳定扰动可以有一个较宽的频谱相对于纵向尺度的大小，特别是，形成非常薄的细丝。所得结果可用于解释天体中稠密冷区的观测结果。
英文摘要：
We investigate thermal instability in an electron-ion magnetized plasma relevant to galaxy clusters, solar corona, and other two-component astrophysical objects. We apply the multicomponent plasma approach when the dynamics of all the species are considered separately through electric field perturbations. General expressions for perturbations obtained in this paper can be applied for a wide range of multicomponent astrophysical and laboratory plasmas also containing the neutrals, dust grains, and other species. We assume that background temperatures of electrons and ions are different and include the energy exchange in thermal equations. We take into account the dependence of collision frequency on density and temperature perturbations. The cooling-heating functions are taken as different ones for electrons and ions. As a specific case, we consider a condensation mode of thermal instability of long-wavelength perturbations when the dynamical time is smaller than a time during which the particles cover the wavelength along the magnetic field due to thermal velocity. We derive a general dispersion relation taking into account the effects mentioned above and obtain simple expressions for growth rates in limiting cases. Perturbations are shown to have an electromagnetic nature. We find that at conditions under consideration transverse scale sizes of unstable perturbations can have a wide spectrum relatively to longitudinal scale sizes and, in particular, form very thin filaments. The results obtained can be useful for interpretation of observations of dense cold regions in astrophysical objects.
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