Dependence of Relativistic Electron Precipitation in the Ionosphere on EMIC Wave Minimum Resonant Energy at the Conjugate Equator
Dependence of Relativistic Electron Precipitation in the Ionosphere on EMIC Wave Minimum Resonant Energy at the Conjugate Equator
复制标题
DOI：
10.1029/2021ja029193
复制
发表时间：
2021-05
期刊：
影响因子：
--
通讯作者：
X.‐J. Zhang;D. Mourenas;Xiao‐Chen Shen;M. Qin;A. Artemyev;Qianli Ma;Wen Li;Mary Hudson;V. Angelopoulos
中科院分区：
文献类型：
--
作者：
X.‐J. Zhang;D. Mourenas;Xiao‐Chen Shen;M. Qin;A. Artemyev;Qianli Ma;Wen Li;Mary Hudson;V. Angelopoulos
我们研究了极地环境卫星（POES）在低地球轨道上探测到的相对论性电子沉淀事件，并与货车艾伦探测器A在地磁赤道附近对电磁离子回旋（EMIC）波的观测密切相关。我们表明，在这些时间内POES记录的>0.7 MeV电子沉淀的发生率强烈增加，当赤道处与氢或氦带EMIC波的回旋共振的最小电子能量降低到1.0-2.5 MeV以下时，达到统计学显著水平，正如准线性理论所预期的那样。氢和氦带EMIC波都可以有效地沉淀MeV电子。然而，当用于与氢带波的回旋共振的最小电子能量较低（Emin = 0.6-1.0 MeV）时，更经常观察到>0.7 MeV的电子沉淀（在统计学显著水平），而当用于与氦带波的回旋共振的最小电子能量稍大（Emin = 1.0-2.5 MeV）时，更经常观察到。这表明了热等离子体对接近He+陀螺频率的波的影响。我们进一步表明，大多数降水事件的能量> 0.7-1.0 MeV，与大多数这些事件期间观察到的EMIC波的回旋共振的估计最小能量（Emin 0.6 - 2.5 MeV）一致。然而，12个探测到的降水事件中有4个不能用观测到的EMIC波的电子准线性散射来解释，20个理论上预期的降水事件中有12个没有被POES探测到，这表明在磁赤道附近可能存在非线性效应，或温暖的等离子体效应，和/或EMIC波的窄局部爆发。
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 (Emin = 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 (Emin = 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 (Emin ∼ 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.