Electromagnetic ion cyclotron (EMIC) waves can very rapidly and effectively scatter relativistic electrons into the atmosphere. EMIC-driven precipitation bursts can be detected by low-altitude spacecraft, and analysis of the fine structure of such bursts may reveal unique information about the near-equatorial EMIC source region. In this study, we report, for the first time, observations of EMIC-driven electron precipitation exhibiting energy, E, dispersion as a function of latitude (and hence L-shell): two predominant categories exhibit dE/dL > 0 and dE/dL < 0. We interpret precipitation with dE/dL < 0 as due to the typical inward radial gradient of cold plasma density and equatorial magnetic field (∼65% of the statistics). Precipitation with dE/dL > 0 is interpreted as due to an outward radial gradient of the equatorial magnetic field, likely produced by energetic ions freshly injected into the ring current (∼35% of the statistics). The observed energy dispersion of EMIC-driven electron precipitation was reproduced in simulations.

中文翻译：

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EMIC 波驱动的电子沉淀：两种类型的能量色散

电磁离子回旋加速器 (EMIC) 波可以非常快速且有效地将相对论性电子散射到大气中。 EMIC驱动的降水爆发可以通过低空航天器探测到，对此类爆发的精细结构的分析可以揭示有关近赤道EMIC源区的独特信息。在这项研究中，我们首次报告了 EMIC 驱动的电子沉淀的观察结果，其表现出能量E、色散作为纬度（以及L壳层）的函数：两个主要类别表现出dE / dL  > 0 和dE / dL  < 0。我们将dE / dL  < 0 的降水解释为冷等离子体密度和赤道磁场的典型向内径向梯度（~65% 的统计数据）。dE / dL > 0的降水 被解释为由于赤道磁场向外的径向梯度，可能是由新注入环电流的高能离子产生的（统计数据的~35%）。在模拟中再现了观察到的 EMIC 驱动电子沉淀的能量分散。