电磁离子回旋体波从Elfin的低海拔角度驱动的能量电子沉淀

论文标题

电磁离子回旋体波从Elfin的低海拔角度驱动的能量电子沉淀

Energetic electron precipitation driven by electromagnetic ion cyclotron waves from ELFIN's low altitude perspective

论文作者

Angelopoulos, V., Zhang, X. -J., Artemyev, A. V., Mourenas, D., Tsai, E., Wilkins, C., Runov, A., Liu, J., Turner, D. L., Li, W., Khurana, K., Wirz, R. E., Sergeev, V. A., Meng, X., Wu, J., Hartinger, M. D., Raita, T., Shen, Y., An, X., Shi, X., Bashir, M. F., Shen, X., Gan, L., Qin, M., Capannolo, L., Ma, Q., Russell, C. L., Masongsong, E. V., Caron, R., He, I., Iglesias, L., Jha, S., King, J., Kumar, S., Le, K., Mao, J., McDermott, A., Nguyen, K., Norris, A., Palla, A., Roosnovo, Tam, J., Xie, E., Yap, R. C., Ye, S., Young, C., Adair, L. A., Shaffer, C., Chung, M., Cruce, P., Lawson, M., Leneman, D., Allen, M., Anderson, M., Arreola-Zamora, M., Artinger, J., Asher, J., Branchevsky, D., Cliffe, M., Colton, K., Costello, C., Depe, D., Domae, B. W., Eldin, S., Fitzgibbon, L., Flemming, A., Frederick, D. M., Gilbert, A., Hesford, B., Krieger, R., Lian, K., McKinney, E., Miller, J. P., Pedersen, C., Qu, Z., Rozario, R., Rubly, M., Seaton, R., Subramanian, A., Sundin, S. R., Tan, A., Thomlinson, D., Turner, W., Wing, G., Wong, C., Zarifian, A.

论文摘要

我们使用来自电子损耗和田间调查（ELFIN）任务中的电磁电磁环（EMIC）波动的能量电子降水（EMIC）的全面观察，这是两个极性低空旋转的立方体，测量50-5000 Kev Electrons，均具有良好的音频分辨率和能量分辨率。 EMIC波驱动的沉淀在沉淀与捕获的通量比的能量光谱图中表现出独特的特征：在0.5 MeV处的峰值（爆发），具有显着的子结构（偶尔降低至次秒时间尺度）。多个Elfin经过相同的MLT扇区，使我们能够研究EMIC波 - 电子相互作用区域的空间和时间演化。使用两年的Elfin数据，我们组装了50个强烈波浪驱动降水事件的统计数据库。大多数居住在黄昏时L = 5-7，而午夜时期的L = 8-12则存在较小的子集。峰值峰值比和半峰降水比（我们的最低共振能量的代理）的能量表现出与基于EMIC波功率谱的先前统计学观察的理论估计值的L壳依赖性。最激烈的事件的降水比的光谱形状远离峰值（即在1.45 meV的两侧）。它也与基于波谱先前统计的准线性扩散理论非常吻合。与强烈的EMIC波驱动的1MEV沉淀同时观察到的Sub-MEV电子沉淀具有光谱形状，这与高度较小的较高频率emic波的有效俯仰角散射至200-300 keV。这些结果证实了emic波在驱动相对论电子损失中的关键作用。非线性效应可能比比皆是，需要进一步研究。

We review comprehensive observations of electromagnetic ion cyclotron (EMIC) wave-driven energetic electron precipitation using data from the energetic electron detector on the Electron Losses and Fields InvestigatioN (ELFIN) mission, two polar-orbiting low-altitude spinning CubeSats, measuring 50-5000 keV electrons with good pitch-angle and energy resolution. EMIC wave-driven precipitation exhibits a distinct signature in energy-spectrograms of the precipitating-to-trapped flux ratio: peaks at 0.5 MeV which are abrupt (bursty) with significant substructure (occasionally down to sub-second timescale). Multiple ELFIN passes over the same MLT sector allow us to study the spatial and temporal evolution of the EMIC wave - electron interaction region. Using two years of ELFIN data, we assemble a statistical database of 50 events of strong EMIC wave-driven precipitation. Most reside at L=5-7 at dusk, while a smaller subset exists at L=8-12 at post-midnight. The energies of the peak-precipitation ratio and of the half-peak precipitation ratio (our proxy for the minimum resonance energy) exhibit an L-shell dependence in good agreement with theoretical estimates based on prior statistical observations of EMIC wave power spectra. The precipitation ratio's spectral shape for the most intense events has an exponential falloff away from the peak (i.e., on either side of 1.45 MeV). It too agrees well with quasi-linear diffusion theory based on prior statistics of wave spectra. Sub-MeV electron precipitation observed concurrently with strong EMIC wave-driven 1MeV precipitation has a spectral shape that is consistent with efficient pitch-angle scattering down to 200-300 keV by much less intense higher frequency EMIC waves. These results confirm the critical role of EMIC waves in driving relativistic electron losses. Nonlinear effects may abound and require further investigation.

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