We investigate relativistic electron precipitation events detected by Polar Environmental Satellites (POES) in low‐Earth orbit in close conjunction with Van Allen Probe A observations of electromagnetic ion cyclotron (EMIC) waves near the geomagnetic equator. We show that the occurrence rate of >0.7 MeV electron precipitation recorded by POES during those times strongly increases, reaching statistically significant levels when the minimum electron energy for cyclotron resonance with hydrogen or helium band EMIC waves at the equator decreases below ≃1.0–2.5 MeV, as expected from the quasi‐linear theory. Both hydrogen and helium band EMIC waves can be effective in precipitating MeV electrons. However, >0.7 MeV electron precipitation is more often observed (at statistically significant levels) when the minimum electron energy for cyclotron resonance with hydrogen band waves is low (E_min = 0.6–1.0 MeV), whereas it is more often observed when the minimum electron energy for cyclotron resonance with helium band waves is slightly larger (E_min = 1.0–2.5 MeV). This is indicative of the warm plasma effects for waves approaching the He⁺ gyrofrequency. We further show that most precipitation events had energies > 0.7–1.0 MeV, consistent with the estimated minimum energy (E_min ∼ 0.6 − 2.5 MeV) of cyclotron resonance with the observed EMIC waves during the majority of these events. However, 4 out of the 12 detected precipitation events cannot be explained by electron quasi‐linear scattering by the observed EMIC waves, and 12 out of 20 theoretically expected precipitation events were not detected by POES, suggesting the possibility of nonlinear effects likely present near the magnetic equator, or warm plasma effects, and/or narrowly localized bursts of EMIC waves.

中文翻译：

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共轭赤道电离层中相对论电子沉淀对EMIC波最小共振能量的依赖性

我们与Van Allen Probe A观测到的地磁赤道附近的电磁离子回旋加速器（EMIC）波密切相关，研究了由极地环境卫星（POES）在近地轨道上检测到的相对论电子降水事件。我们显示，在这段时间内，POES记录的> 0.7 MeV电子沉淀的发生率急剧增加，当与赤道上的氢或氦带EMIC波回旋共振的最小电子能量降低到≃1.0–2.5 MeV以下时，达到统计上显着的水平。 ，这是拟线性理论所期望的。氢和氦带的EMIC波都可以有效地沉淀MeV电子。但是，> 0。E _min  = 0.6–1.0 MeV），而在氦带波回旋加速器共振的最小电子能量稍大时（E _min  = 1.0–2.5 MeV），这种情况更常见。这表明接近He ⁺陀螺频率的波具有温暖的等离子体效应。我们进一步表明，大多数降水事件的能量> 0.7–1.0 MeV，与估计的最小能量（E _min 在大多数这些事件中，所观察到的EMIC波的回旋共振约为0.6-2.5 MeV）。但是，在12个探测到的降水事件中，有4个无法用观测到的EMIC波解释电子准线性散射，而在POES上没有探测到20个理论上预期的降水事件中的12个，这表明可能存在非线性效应。电磁赤道，或温暖的等离子体效应，和/或EMIC波的狭窄局部爆发。