Effects of cold electron density on the whistler anisotropy instability
Effects of cold electron density on the whistler anisotropy instability
复制标题
冷电子密度对惠斯勒各向异性不稳定性的影响
DOI：
10.1029/2012ja018402
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发表时间：
2013
期刊：
影响因子：
--
通讯作者：
W. Li
中科院分区：
文献类型：
--
作者：
S. Wu;R. Denton;W. Li
我们确认结果从以前的推导平行传播的哨声波不稳定性的线性增长率时，冷和热的人口存在，并扩展以前的方程来描述的空间增长率。对于中等的等离子体β，总的等离子体密度的热等离子体密度的比率的主导模式的线性增长率总是有一个峰值。对于高各向异性Δ hot = T hot/T hot − 1，线性对流增长率有类似的峰值，但对于低各向异性则没有。我们提出了这些结果的一个大范围的物理参数。我们的结果可以用来快速确定增长率是否会增加或减少冷等离子体密度，我们证明了这一点最近观察到的事件。我们解释的观察，更大的冷等离子体密度导致波的中心频率下降。模型方程可以用来预测最大的时间和空间增长率的最佳冷等离子体密度。一个相对论电磁等离子体色散代码被用来表明，分析公式是大致正确的，在附近的最佳冷密度，除非热速度是高度相对论的<$0.5 c，其中c是光速。与电磁色散程序WHAMP的比较表明，对于实际的各向异性，我们的公式对于β_（？）
We confirm results from a previous derivation of the linear growth rate of the parallel propagating whistler wave instability when both cold and hot populations are present, and extend previous equations to describe the spatial growth rate. For moderate plasma beta, there is always a peak in the linear growth rate of the dominant mode with respect to the ratio of total plasma density to the hot plasma density. There is a similar peak in the linear convective growth rate for high anisotropy Ahot = T⊥ hot/T∥ hot − 1 but not for low anisotropy. We present these results for a large range of physical parameters. Our results can be used to quickly determine whether the growth rate will increase or decrease with respect to cold plasma density, and we demonstrate this for an event observed recently. We explain the observation that greater cold plasma density leads to a drop in the central frequency of the waves. Model equations can be used to predict the optimal cold plasma density for maximum temporal and spatial growth rate. A relativistic electromagnetic plasma dispersion code is used to show that the analytical formulas are roughly correct in the vicinity of the optimal cold density unless the thermal velocity is highly relativistic ∼0.5 c, where c is the speed of light. Comparison with the electromagnetic dispersion code WHAMP shows that our formulas are adequate for β∥ hot < 1 for realistic anisotropy.