无碰撞等离子体环境中反束流和温度各向异性驱动的非周期电子不稳定性的比较
Comparing the counter-beaming and temperature anisotropy driven aperiodic electron firehose instabilities in collisionless plasma environments
摘要：
电子消防管不稳定性是研究最多的动力学不稳定性之一，特别是在空间等离子体中，其动力学主要由无碰撞的波粒相互作用控制。本文对由各向异性温度和电子反束布居数激发的非周期电子水龙带不稳定性进行了比较分析。两个对称的反束提供了类似于单个（非漂移）布居的温度各向异性的有效动力学各向异性，其中沿磁场方向的温度大于垂直方向的温度。因此，反束流等离子体容易受到类似消防软管的不稳定性（FIs），平行和倾斜的分支。在这里，我们专注于倾斜的光束FI，这也是非周期性的自由能时，对称的反光束提供。研究结果表明，当漂移或聚束速度（$U$）不超过热速度（$α$）时，在相同的波数区间和相同的倾斜角度范围内（相对于磁场方向），存在非周期性聚束，但反聚束聚束.然而，对于$U/α> 1$，还预测了另一种静电双流不稳定性（ETSI），其增长率可能高于CBFI，并且在这种情况下可能主导动力学。
英文摘要：
The electron firehose instabilities are among the most studied kinetic instabilities, especially in the context of space plasmas, whose dynamics is mainly controlled by collisionless wave-particle interactions. This paper undertakes a comparative analysis of the aperiodic electron firehose instabilities excited either by the anisotropic temperature or by the electron counter-beaming populations. Two symmetric counter-beams provide an effective kinetic anisotropy similar to the temperature anisotropy of a single (non-drifting) population, with temperature along the magnetic field direction larger than that in perpendicular direction. Therefore, the counter-beaming plasma is susceptible to firehose-like instabilities (FIs), parallel and oblique branches. Here we focus on the oblique beaming FI, which is also aperiodic when the free energy is provided by symmetric counter-beams. Our results show that, for relative small drifts or beaming speeds ($U$), not exceeding the thermal speed ($α$), the aperiodic FIs exist in the same interval of wave-numbers and the same range of oblique angles (with respect to the magnetic field direction), but the growth rates of counter-beaming FI (CBFI) are always higher than those of temperature anisotropy FI (TAFI). For $U/α> 1$, however, another electrostatic two-stream instability (ETSI) is also predicted, which may have growth rates higher than those of CBFI, and may dominate in that case the dynamics.
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