Parametric analysis of pitch angle scattering and losses of relativistic electrons by oblique EMIC waves
Parametric analysis of pitch angle scattering and losses of relativistic electrons by oblique EMIC waves
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DOI：
10.3389/fspas.2023.1163515
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发表时间：
2023-04
期刊：
影响因子：
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通讯作者：
M. Hanzelka;Wen Li;Q. Ma
中科院分区：
文献类型：
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作者：
M. Hanzelka;Wen Li;Q. Ma
这项研究分析了电子离子回旋（EMIC）波对地球外辐射带中相对论电子散射的影响，并且已知在磁层内观察到EMIC的损失。放大器和波动角度并评估对这两个参数的高级散射行为的敏感性，包括非常倾斜的传播的可能性。令人惊讶的是，最近讨论了在低螺距角度上的力束效应和相关的强积极广告，这不会导致降水电子的相空间密度降低，并且证明电子将损失锥传输到损失锥体中的散射中，从损失锥体中散发出损失，但要远离传播的损失。非线性分数共振和理论分析表明，这些共振可能有助于亚层压电子降水，但可能会被非谐波效应所掩盖。
This study analyzes the effects of electromagnetic ion cyclotron (EMIC) waves on relativistic electron scattering and losses in the Earth’s outer radiation belt. EMIC emissions are commonly observed in the inner magnetosphere and are known to reach high amplitudes, causing significant pitch angle changes in primarily > 1 MeV electrons via cyclotron resonance interactions. We run test-particle simulations of electrons streaming through helium band waves with different amplitudes and wave normal angles and assess the sensitivity of advective and diffusive scattering behaviors to these two parameters, including the possibility of very oblique propagation. The numerical analysis confirms the importance of harmonic resonances for oblique waves, and the very oblique waves are observed to efficiently scatter both co-streaming and counter-streaming electrons. However, strong finite Larmor radius effects limit the scattering efficiency at high pitch angles. Recently discussed force-bunching effects and associated strong positive advection at low pitch angles are, surprisingly, shown to cause no decrease in the phase space density of precipitating electrons, and it is demonstrated that the transport of electrons into the loss cone balances out the scattering out of the loss cone. In the case of high-amplitude obliquely propagating waves, weak but non-negligible losses are detected well below the minimum resonance energy, and we identify them as the result of non-linear fractional resonances. Simulations and theoretical analysis suggest that these resonances might contribute to subrelativistic electron precipitation but are likely to be overshadowed by non-resonant effects.