Electrostatic bursts generated by electrons in Landau Resonance with whistler mode chorus
Electrostatic bursts generated by electrons in Landau Resonance with whistler mode chorus
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朗道共振中电子产生的静电爆发与口哨模式合唱
DOI：
10.1029/ja088ia04p03079
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发表时间：
1983
影响因子：
--
通讯作者：
T. Eastman
中科院分区：
文献类型：
--
作者：
L. Reinleitner;D. Gurnett;T. Eastman
最近对来自ISEE 1和ISEE 2航天器的宽带等离子体波数据的研究表明，地球外磁层中的哨声模式合唱发射往往伴随着频率略低于电子等离子体频率的静电波高频爆发。研究表明，在某些情况下，静电波调制在合唱频率。利用ISEE 1上的等离子体分析仪（LEPEDEA）数据进行的进一步研究表明，这些爆发是由一束电子与合唱波发生朗道（纵向）共振，从而以合唱相速度移动而产生的。在合唱强度中存在一个阈值，低于该阈值，静电爆发不会出现。高频静电波被认为是由一种称为电阻介质不稳定性的双流不稳定性引起的。电阻性介质不稳定性的特征在于静电猝发频率降低到电子等离子体频率以下。不稳定性仅适用于V0/VT为1的量级的情况，其中V0是束的速度，VT是等离子体电子的平均热速度。我们的推导假定冷离子而热电子。这种不稳定性需要朗道阻尼来起作用。因此，束流速度必须在电子分布函数的陡斜率区域，而不是在高速尾部区域。在LEPEDEA数据检查的情况下，电子热能是几百eV的数量级。在所观察到的情况下，电子束的速度为10400 eV和10630 eV，从而验证了静电爆发是在适当的制度的电阻介质的不稳定性。
Recent studies of wideband plasma wave data from the ISEE 1 and ISEE 2 spacecraft have revealed that whistler mode chorus emissions in the earth's outer magnetosphere are often accompanied by high-frequency bursts of electrostatic waves with a frequency slightly below the electron plasma frequency. Investigations have shown that in some cases the electrostatic waves are modulated at the chorus frequency. Further studies using the plasma analyzer (LEPEDEA) data on ISEE 1 indicate that these bursts are produced by a ‘beam’ of electrons in Landau (longitudinal) resonance with the chorus wave and thus moving at the chorus phase velocity. A threshold exists in the chorus intensity below which the electrostatic bursts do not appear. The high-frequency electrostatic waves are believed to be caused by a type of two-stream instability called the resistive medium instability. The resistive medium instability is characterized by a reduction in the electrostatic burst frequency below the electron plasma frequency, The instability is applicable only in the regime where V0/VT is on the order of 1, where V0 is the velocity of the beam and VT is the average thermal velocity of the plasma electrons. Our derivation assumes cold ions but warm electrons. The instability requires Landau damping to operate. Thus the beam velocity must be in the region of steep slope on the electron distribution function rather than in the high-velocity tail region. In the cases examined from the LEPEDEA data the electron thermal energies are on the order of a few hundred eV. The beam velocities in the observed cases were ≈ 400 eV and ≈ 630 eV, thus verifying that the electrostatic bursts are in the proper regime for the resistive medium instability.