Trapping and Amplification of Unguided Mode EMIC Waves in the Radiation Belt
Trapping and Amplification of Unguided Mode EMIC Waves in the Radiation Belt
复制标题
辐射带中非导模EMIC波的捕获和放大
DOI：
10.1029/2021ja029322
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发表时间：
2021
期刊：
影响因子：
--
通讯作者：
Zhang T. L.
中科院分区：
文献类型：
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作者：
Wang G.;Gao Z. L.;Wu M. Y.;Wang G. Q.;Xiao S. D.;Chen Y. Q.;Zou Z. Y.;Zhang T. L.
电磁离子回旋（EMIC）波会引起辐射带中相对论电子的散射损耗。根据波的传播特性，它们可以分为导模和非导模。辐射带中的导模波已得到广泛的研究，但对非导模波的观测还没有得到预期。根据货车艾伦探针的观测结果，根据偏振特性，首次证明了辐射带中存在强非导L模EMIC波。增长率分析表明，能量为几百keV的热质子可以提供波增长的自由能。当质子丰度比随L-壳层急剧下降时，由局域氦截止频率的空间位置形成的反射界面可以近似平行于赤道面。这种结构与热质子相结合可能导致非导模波的捕获和显着放大。这些结果有助于理解辐射带中EMIC波的性质及其动力学。
Electromagnetic ion cyclotron (EMIC) waves can cause the scattering loss of the relativistic electrons in the radiation belt. They can be classified into the guided mode and the unguided mode, according to wave's propagation behavior. The guided mode waves have been widely investigated in the radiation belt, but the observation of the unguided mode waves have not been expected. Based on the observations of Van Allen Probes, we demonstrate for the first time the existence of the intense unguided L‐mode EMIC waves in the radiation belt according to the polarization characteristics. Growth rate analyses indicate that the hot protons with energies of a few hundred keV may provide the free energy for wave growth. The reflection interface formed by the spatial locations of local helium cutoff frequencies can be nearly parallel to the equatorial plane when the proton abundance ratio decreases sharply with L ‐shell. This structure combined with hot protons may lead to the trapping and significant amplification of the unguided mode waves. These results may help to understand the nature of EMIC waves and their dynamics in the radiation belt.