冷氧离子在离子波生长中的作用

IF 2.9 2区 地球科学 Q2 ASTRONOMY & ASTROPHYSICS
Shujie Gu, Misa Cowee, Xiangrong Fu, Lunjin Chen, Xu Liu, Vania Jordanova
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引用次数: 0

摘要

电磁离子回旋波是由地球磁层环电流离子温度各向异性驱动的,在辐射带中加速和沉淀相对论性电子中起着关键作用。它们的激发和饱和受周围冷等离子体的显著影响。先前的研究表明,背景冷氦离子可以影响EMIC波的生长和饱和,但冷氧离子在波饱和中的作用仍然知之甚少。本文采用线性理论和非线性混合模拟方法,研究了冷氧离子对含冷热质子、冷氦离子和冷氧离子的均匀等离子体中主波生长和饱和的影响。我们的研究结果表明,增加冷氧离子浓度会降低EMIC波的增长速度,并使氦和氧回旋频率附近的停止带的光谱宽度变宽。此外,在以氦带为主的情况下,氧离子浓度的增加显著降低了主位波的饱和振幅,而以氢带为主的情况下则不受影响。冷离子在波激发过程中被加热,冷氦离子被加热到keV能量,比冷质子和氧离子更明显。随着冷氧离子浓度的增加,冷氦离子被加热到keV能量所需的时间变长。这些结果提供了对冷等离子体如何改变EMIC波的光谱特性和振幅的见解,揭示了通过EMIC波从热质子到冷等离子体的能量转移。
本文章由计算机程序翻译,如有差异,请以英文原文为准。
The Role of Cold Oxygen Ions in the EMIC Wave Growth

Electromagnetic ion cyclotron (EMIC) waves, driven by ring current ion temperature anisotropy in the Earth's magnetosphere, play a key role in accelerating and precipitating relativistic electrons in the radiation belts. Their excitation and saturation are significantly affected by the surrounding cold plasma. Previous studies have shown that background cold helium ions can influence the growth and saturation of EMIC waves, yet the role of cold oxygen ions in wave saturation remains less understood. In this paper, we use linear theory and nonlinear hybrid simulation to investigate the effect of cold oxygen ions in the EMIC wave growth and saturation in a homogeneous plasma containing hot and cold protons, cold helium and cold oxygen ions. Our findings reveal that increasing the cold oxygen ion concentration decreases the EMIC wave growth rate and broadens the spectral width of stop bands near the helium and oxygen gyrofrequencies. Furthermore, an increasing oxygen ion concentration notably reduces the saturation amplitude of EMIC waves in cases where the helium band is dominant, while cases with a dominant hydrogen band remain unaffected. Cold ions are heated during wave excitation, and cold helium ions are heated to keV energy, more significantly than cold protons and oxygen ions. With cold oxygen ion concentration increasing, cold helium ions take longer time to be heated to keV energy. These results offer insights into how cold plasma modifies the spectral properties and amplitudes of EMIC waves, shedding light on energy transfer from hot protons to cold plasma through EMIC waves.

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来源期刊
Journal of Geophysical Research: Space Physics
Journal of Geophysical Research: Space Physics Earth and Planetary Sciences-Geophysics
CiteScore
5.30
自引率
35.70%
发文量
570
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