Statistical Study of Approaching Strong Diffusion of Low-Energy Electrons by Chorus and ECH Waves Based on In Situ Observations
Statistical Study of Approaching Strong Diffusion of Low-Energy Electrons by Chorus and ECH Waves Based on In Situ Observations
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DOI：
10.1029/2022ja030269
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发表时间：
2022-03-01
影响因子：
2.8
通讯作者：
Jun, C. -W.
中科院分区：
文献类型：
--
作者：
Fukizawa, M.;Sakanoi, T.;Jun, C. -W.
磁层内电子通过低频合唱（LBC）、高频合唱（UBC）和静电电子回旋谐波（ECH）的俯仰角（PA）散射沉淀在电离层中。然而，PA散射效率的低能量电子（0.1-10千电子伏）尚未通过原位观测，因为在磁层内的损失锥通量测量的困难进行了研究。在这项研究中，我们证明，LBC，UBC，和ECH波有助于PA散射的电子在不同的能量范围内使用Arase（ERG）卫星观测数据，并相继检测到中等损失锥填充，即接近强扩散。LBC、UBC和ECH波分别在类似于2-20 keV、类似于1-10 keV和类似于0.1-2 keV处接近强扩散。高幅LBC（>50 pT）、UBC（>20 pT）和ECH（>10 mV/m）波的接近强扩散的发生率分别达到约70%、约40%和约30%，高于无同时波活动的情况。出现率高的能量范围与基于准线性理论的PA扩散率超过强扩散水平的范围一致。
Inner magnetospheric electrons are precipitated in the ionosphere via pitch-angle (PA) scattering by lower band chorus (LBC), upper band chorus (UBC), and electrostatic electron cyclotron harmonic (ECH) waves. However, the PA scattering efficiency of low-energy electrons (0.1-10 keV) has not been investigated via in situ observations because of difficulties in flux measurements within loss cones at the magnetosphere. In this study, we demonstrate that LBC, UBC, and ECH waves contribute to PA scattering of electrons at different energy ranges using the Arase (ERG) satellite observation data and successively detected the moderate loss cone filling, that is, approaching strong diffusion. Approaching strong diffusion by LBC, UBC, and ECH waves occurred at similar to 2-20 keV, similar to 1-10 keV, and similar to 0.1-2 keV, respectively. The occurrence rate of the approaching strong diffusion by high-amplitude LBC (>50 pT), UBC (>20 pT), and ECH (>10 mV/m) waves, respectively, reached similar to 70%, similar to 40%, and similar to 30% higher than that without simultaneous wave activity. The energy range in which the occurrence rate was high agreed with the range where the PA diffusion rate of each wave exceeded the strong diffusion level based on the quasilinear theory.