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所属单位：航天学院

发表刊物：Phys. Plasmas

摘要：Heavy ions (O+ and He+) are an important constituent of plasma sheets. They are most significant during geomagnetic quiet periods when charge-exchange reactions result in a faster loss of H+ ions than heavy ions. With inward injections of energetic particles from the plasma sheet into the inner magnetosphere, heavy ions play a key role in producing the ring current and radiation belt. In this work, we investigate the acceleration of heavy ions by electromagnetic ion cyclotron (EMIC) waves, which has been recently observed in the near-Earth plasma sheet. Nonlinear motion of ions, including phase trapping and strong acceleration, can be induced by EMIC waves through cyclotron resonance. The frozen-in condition of the plasma is not satisfied in this process. The results of test particle simulations show that heavy ions following wave-induced nonlinear motion from L = 5-7 increase from 36% of the total test particles to 44%. The He+ ions at L = 5 can be accelerated to as much as ten times the initial energy of 30 keV. The attainable energy increase ΔEk depends on the L value and the ion composition. An abundance of heavy ions in the background plasma lowers ΔEk. This effect is more prominent farther out in the plasma sheet. Nonlinear phase trapping occurs when ions are accelerated, and stronger acceleration corresponds to a smaller trapping zone. Hence, wave-induced acceleration is closely associated with the redistribution of ions in their phase space. Heavy ions in the plasma sheet have an important impact on inner magnetosphere dynamics, and thus, EMIC waves should not be neglected in plasma sheet energization. © 2019 Author(s).

ISSN号：1070-664X

是否译文：否

发表时间：2019-02-01

合写作者：Sun, Kang,Zhang, Yusheng,Zhai, Hao

通讯作者：王志强