Electron scattering by whistler-mode ELF hiss in
Electron scattering by whistler-mode ELF hiss in
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DOI：
10.1029/2007ja012678
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发表时间：
2008-04
期刊：
影响因子：
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通讯作者：
D. Summers;B. Ni;N. Meredith;R. Horne;R. Thorne;M. Moldwin;R. R. Anderson-R.;R. R. Anderson-R.;R. Horne;N. Meredith
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文献类型：
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作者：
D. Summers;B. Ni;N. Meredith;R. Horne;R. Thorne;M. Moldwin;R. R. Anderson-R.;R. R. Anderson-R.;R. Horne;N. Meredith
辐射带高能电子的非绝热损失过程包括各种磁层等离子体波模式的俯仰角散射对大气的降水损失。在这里，我们考虑了等离子体层羽流中哨子模极低频嘶嘶声的俯仰角散射引起的电子沉淀损失。利用波观测和从联合释放和辐射效应卫星(CRRES)上的等离子体波实验中推断的等离子体密度，我们分析了可以获得良好确定的HISS光谱强度的羽流间隔。然后我们选择了14个具有代表性的羽流进行详细的研究，其中包括10个黄昏侧羽流和4个非黄昏侧羽流，局部嘶嘶声的幅度从最大值大于300PT到最小值小于1PT不等。我们估计了每个所选羽流中由HISS的俯仰角散射引起的电子损失时间尺度τ损失作为L壳层和电子能量的函数；τ损失由准线性理论计算为赤道损失锥角下的反弹平均扩散速率的倒数。我们发现，羽流中嘶嘶声的俯仰角散射可以有效地引起能量在100keV到1 MeV范围内的外区电子的沉淀损失，尽管τ损失的大小可以高度依赖于波功率、L壳层和电子能量。对于100keV至200keV电子，通常为τLoss∼1天，而最小损耗时间刻度(τLoss)为∼小时。对于500keV到1 MeV的电子，通常(τ损耗)分钟∼天，而在大波幅的情况下(τ损耗)分钟<；1天(∼100‘S PT)。除了引起MeV电子的直接沉淀损失外，羽流中的HISS散射还可能通过耗尽较低能量的电子种子数来减少MeV电子的产生。外区电子通量动态变化的模型应考虑等离子体层羽流中ELF嘶嘶散射引起的电子沉淀损失。
Nonadiabatic loss processes of radiation belt energetic electrons include precipitation loss to the atmosphere due to pitch-angle scattering by various magnetospheric plasma wave modes. Here we consider electron precipitation loss due to pitch-angle scattering by whistler-mode ELF hiss in plasmaspheric plumes. Using wave observations and inferred plasma densities from the Plasma Wave Experiment on the Combined Release and Radiation Effects Satellite (CRRES), we analyze plume intervals for which well-determined hiss spectral intensities are available. We then select 14 representative plumes for detailed study, comprising 10 duskside plumes and 4 nonduskside plumes, with local hiss amplitudes ranging from maximum values of above 300 pT to minimum values of less than 1 pT. We estimate the electron loss timescale τ loss due to pitch-angle scattering by hiss in each chosen plume as a function of L-shell and electron energy; τ loss is calculated from quasi-linear theory as the inverse of the bounce-averaged diffusion rate evaluated at the equatorial loss cone angle. We find that pitch-angle scattering by hiss in plumes can be efficient for inducing precipitation loss of outer-zone electrons with energies throughout the range 100 keV to 1 MeV, though the magnitude of τ loss can be highly dependent on wave power, L-shell, and electron energy. For 100- to 200-keV electrons, typically τ loss ∼ 1 day while the minimum loss timescale (τ loss ) min ∼ hours. For 500-keV to 1-MeV electrons, typically (τ loss ) min ∼ days, while (τ loss ) min < 1 day in the case of large wave amplitude (∼100's pT). Apart from inducing direct precipitation loss of MeV electrons, scattering by hiss in plumes may reduce the generation of MeV electrons by depleting the lower energy electron seed population. Models of the dynamical variation of the outer-zone electron flux should incorporate electron precipitation loss induced by ELF hiss scattering in plasmaspheric plumes.