Electrostatic wave growth: secondary peaks in a measured auroral electron distribution function
Electrostatic wave growth: secondary peaks in a measured auroral electron distribution function
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静电波增长：测量的极光电子分布函数中的次级峰值
DOI：
10.1029/ja085ia04p01713
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发表时间：
1980
影响因子：
--
通讯作者：
R. Kaufmann
中科院分区：
文献类型：
--
作者：
R. Kaufmann
在火箭飞越明亮的极光时，经常在高能（25 eV <E <15 keV）电子分布函数中测量到小的次级峰。本文分析了一个在250 km处测量的样本分布函数。分析的目的是观察所观察到的次级峰是否足够大以驱动静电不稳定性。详细分析了分布函数的两个具体特征：第二个平行峰，其特征在于正的Δ f/Δ v Δ的区域，和第二个垂直峰，其特征在于正的Δ f/Δ v Δ。平行峰产生静电哨声和离子回旋波的正增长率，但这些增长率太小，在电弧内产生显着的波幅。当静电电子回旋波和上混杂波相互作用时，垂直峰产生更大的增长率。我们的结论是，垂直峰是最后一个功能，产生强烈的不稳定性，因为电子向下移动到火箭。当火箭到达ωUH = 2的高度时，应该看到最大的波浪|ωce|.在250公里处检测到的等离子体似乎已经发展到由垂直峰驱动的波的生长长度与弧的尺寸相当。一旦产生，上混合波和电子回旋波也将与具有小螺距角的电子共振，因此它们可以将平行峰扩展到远远超过其产生显著增长率的点。
Small secondary peaks are frequently measured in energetic (25 eV <E <15 keV) electron distribution functions during rocket flights over bright auroras. One sample distribution function that was measured at 250 km is analyzed in this paper. The purpose of the analysis is to see if the observed secondary peaks are large enough to drive electrostatic instabilities. Two specific features of the distribution function are analyzed in detail: a secondary parallel peak, characterized by a region of positive ∂f/∂ν∥, and a secondary perpendicular peak, characterized by positive ∂f/∂ν⊥. The parallel peak produces positive growth rates for electrostatic whistler and ion cyclotron waves, but these growth rates are too small to generate significant wave amplitudes within an arc. The perpendicular peak produces much larger growth rates for electrostatic electron cyclotron and upper hybrid waves when these two modes are interacting. We conclude that the perpendicular peak was the last feature to produce a strong instability as the electrons moved down to the rocket. The largest waves should be seen as rockets reach an altitude where ωUH = 2|ωce|. The plasma detected at 250 km appears to have evolved until the growth lengths of waves that are driven by the perpendicular peak are comparable to the dimension of an arc. Once generated, the upper hybrid and electron cyclotron waves will also resonate with electrons which have small pitch angles, and they can therefore spread the parallel peak well beyond the point at which it produces significant growth rates.