Electron Scattering by Very‐Low‐Frequency and Low‐Frequency Waves From Ground Transmitters in the Earth's Inner Radiation Belt and Slot Region
Electron Scattering by Very‐Low‐Frequency and Low‐Frequency Waves From Ground Transmitters in the Earth's Inner Radiation Belt and Slot Region
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DOI：
10.1029/2022ja030349
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发表时间：
2022-06
期刊：
影响因子：
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通讯作者：
Q. Ma;W. Gu;S. Claudepierre;W. Li;J. Bortnik;M. Hua;X. Shen
中科院分区：
文献类型：
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作者：
Q. Ma;W. Gu;S. Claudepierre;W. Li;J. Bortnik;M. Hua;X. Shen
来自地面发射器的甚低频（VLF）和低频（LF）波在电离层波导中传播，其部分功率泄漏到地球的内部辐射带和缝隙区域，在那里可能导致电子沉淀损失。利用货车艾伦探测器的观测结果，我们对频率为14至200 kHz的VLF和LF发射波进行了调查。得到了1 < L < 3时电磁波的统计振幅和频谱。基于最近对甚低频发射波传播的研究，我们将总的波功率分为管道和未管道部分，并建立了未管道波的波法线角与L壳、磁纬度和波频率的依赖关系模型。在低频时，无导管波沿着垂直方向发射，波的法向角在传播过程中逐渐增大，直至达到Gendrin角;在高频时，无导管波的法向角随Gendrin角的变化而变化。我们计算了由于导管和未导管的VLF和LF波的电子的反弹平均俯仰角和动量扩散系数。无导管波和导管波分别在L = 1.5和2.5处引起有效的俯仰角散射。虽然地面发射器在高于30 kHz的频率下的波功率很低，但这些波可以引起较低能量（L = 1.5时为2-200 keV）电子的俯仰角散射，这些电子不能与频率低于30 kHz的VLF发射器波、闪电产生的哨声或等离子体层嘶嘶声共振。
The very‐low frequency (VLF) and low frequency (LF) waves from ground transmitters propagate in the ionospheric waveguide, and a portion of their power leaks to the Earth's inner radiation belt and slot region where it can cause electron precipitation loss. Using Van Allen Probes observations, we perform a survey of the VLF and LF transmitter waves at frequencies from 14 to 200 kHz. The statistical electric and magnetic wave amplitudes and frequency spectra are obtained at 1 < L < 3. Based on a recent study on the propagation of VLF transmitter waves, we divide the total wave power into ducted and unducted portions, and model the wave normal angle of unducted waves with dependences on L shell, magnetic latitude, and wave frequency. At lower frequencies, the unducted waves are launched along the vertical direction and the wave normal angle increases during the propagation until reaching the Gendrin angle; at higher frequencies, the normal angle of unducted waves follows the variation of Gendrin angle. We calculate the bounce‐averaged pitch angle and momentum diffusion coefficients of electrons due to ducted and unducted VLF and LF waves. Unducted and ducted waves cause efficient pitch angle scattering at L = 1.5 and 2.5, respectively. Although the wave power from ground transmitters at frequencies higher than 30 kHz is low, these waves can cause the pitch angle scattering of lower energy (2–200 keV at L = 1.5) electrons, which cannot resonate with the VLF transmitter waves at frequencies below 30 kHz, lightning generated whistlers, or plasmaspheric hiss.