Triggering process of electromagnetic ion cyclotron rising tone emissions in the inner magnetosphere
Triggering process of electromagnetic ion cyclotron rising tone emissions in the inner magnetosphere
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DOI：
10.1002/jgra.50523
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发表时间：
2013-09-01
影响因子：
2.8
通讯作者：
Omura, Yoshiharu
中科院分区：
文献类型：
--
作者：
Shoji, Masafumi;Omura, Yoshiharu
航天器的观测和模拟表明，产生相干电磁离子回旋（EMIC）触发的发射与上升的音调频率。在内磁层中，具有大温度各向异性的高能质子会自发激发EMIC波。我们再现了EMIC触发的排放在地球的磁层的真实的规模混合模拟与圆柱形磁几何。我们得到了自发触发的非线性EMIC波，其频率在EMIC色散关系的H（+）带上升。在相空间中形成质子空穴。我们还导出了EMIC非线性波增长触发过程的理论最佳波幅。最佳波振幅和非线性过渡时间与模拟结果吻合较好。在有限时间内的非线性波增长形成了上升音发射的子包结构。子包的形成过程是重复的，因为一个新的触发波产生的相位组织的质子，这是从以前的子包释放。然后，EMIC触发发射形成为在不同上升频率下生成的子分组的序列。
Spacecraft observations and simulations show generation of coherent electromagnetic ion cyclotron (EMIC) triggered emissions with rising tone frequencies. In the inner magnetosphere, the spontaneously triggered EMIC waves are generated by the energetic protons with large temperature anisotropy. We reproduced EMIC triggered emissions in the Earth's magnetosphere by real scale hybrid simulations with cylindrical magnetic geometry. We obtained spontaneously triggered nonlinear EMIC waves with rising frequencies in the H(+)band of the EMIC dispersion relation. The proton holes in the phase space are formed. We have also derived the theoretical optimum wave amplitude for triggering process of the EMIC nonlinear wave growth. The optimum wave amplitude and the nonlinear transition time show a good agreement with the present simulation result. The nonlinear wave growth over a limited time forms a subpacket structure of a rising tone emission. The formation process of a subpacket is repeated because of a new triggering wave generated by the phase-organized protons, which are released from the previous subpacket. Then, the EMIC triggered emission is formed as a train of subpackets generated at different rising frequencies.