Energetic Electron Precipitation Driven by the Combined Effect of ULF, EMIC, and Whistler Waves
Energetic Electron Precipitation Driven by the Combined Effect of ULF, EMIC, and Whistler Waves
复制标题
DOI：
10.1029/2021ja029871
复制
发表时间：
2022-01-01
影响因子：
2.8
通讯作者：
Angelopoulos, Vassilis
中科院分区：
文献类型：
--
作者：
Bashir, M. Fraz;Artemyev, Anton;Angelopoulos, Vassilis
高能电子在地球内磁层的损失主要是由向外的径向扩散和散射到大气中的各种电磁波。负责电子散射的两种最重要的波模式是电磁离子回旋（EMIC）波和哨声模式波（哨声波），它们一起作用，可以在从几keV到几MeV的宽能量范围内提供快速的电子损失。波粒共振相互作用导致电子散射是很好地描述准线性扩散理论使用冷等离子体色散，而非线性共振和热等离子体色散的影响是不太好理解。本研究的目的是检查这些影响，并估计其意义的一个特定的事件，在此期间，两个波模式是准周期性调制的超低频（ULF）压缩波。EMIC和哨声波振幅的这种调制提供了一个独特的机会，比较非线性共振散射（重要的最强烈的波）与准线性扩散（占主导地位的低强度波）。等离子体特性的相同调制允许更好地表征热等离子体对EMIC波色散的影响。虽然热等离子体效应显着增加的最小共振能量，E-min，最强烈的EMIC波，这样的影响变得可以忽略不计的高频部分的氢带EMIC波谱。通过与哨声波共振的300-500 keV电子的非线性相位捕获可以加速并使它们与EMIC波共振，EMIC波又将这些电子快速散射到损失锥中。我们的研究结果突出了非线性效应的重要性，在磁层内的高能电子通量的模拟。
Energetic electron losses in the Earth's inner magnetosphere are dominated by outward radial diffusion and scattering into the atmosphere by various electromagnetic waves. The two most important wave modes responsible for electron scattering are electromagnetic ion cyclotron (EMIC) waves and whistler-mode waves (whistler waves) that, acting together, can provide rapid electron losses over a wide energy range from few keV to few MeV. Wave-particle resonant interaction resulting in electron scattering is well described by quasi-linear diffusion theory using the cold plasma dispersion, whereas the effects of nonlinear resonances and hot plasma dispersion are less well understood. This study aims to examine these effects and estimate their significance for a particular event during which both wave modes are quasi-periodically modulated by ultra-low-frequency (ULF) compressional waves. Such modulation of EMIC and whistler wave amplitudes provides a unique opportunity to compare nonlinear resonant scattering (important for the most intense waves) with quasi-linear diffusion (dominant for low-intensity waves). The same modulation of plasma properties allows better characterization of hot plasma effects on the EMIC wave dispersion. Although hot plasma effects significantly increase the minimum resonant energy, E-min, for the most intense EMIC waves, such effects become negligible for the higher frequency part of the hydrogen-band EMIC wave spectrum. Nonlinear phase trapping of 300-500 keV electrons through resonances with whistler waves may accelerate and make them resonant with EMIC waves that, in turn, quickly scatter those electrons into the loss-cone. Our results highlight the importance of nonlinear effects for simulations of energetic electron fluxes in the inner magnetosphere.