低频嘶声和电磁离子回旋波对辐射带电子的弹跳共振散射效应研究

Wave-particle interactions play a crucial role in the dynamic evolution of radiation belt electrons. Corresponding to three types of periodic motion of charged particles trapped by the Earth's magnetic field, resonant interactions between magnetospheric waves and radiation belt electrons also have three basic mechanisms: cyclotron, bounce and drift resonances. While the cyclotron and drift resonances have been well studied, little attention has been paid to bounce resonance. It has been found that both low-frequency hiss and electromagnetic ion cyclotron waves can resonate with radiation belt electrons and result in strong pitch angle scattering of high pitch angle electrons. However, the energy scattering effects on electrons and combined scattering effects by these two waves have not been quantified. Based on the bounce resonance linear theory, this project will perform a comprehensive study on the pitch angle and energy scattering of electrons by low-frequency hiss and electromagnetic ion cyclotron waves, as well as their combined scattering effects. The test-particle simulations will be adopted to investigate the resonant region in which the linear theory is applicable. Bounce resonant interactions will be further incorporated into the current radiation belt model to quantify the combined and respective roles of EMIC wave and low-frequency hiss induced bounce resonance scattering in the radiation belt electron dynamics.

波粒相互作用在辐射带电子动态演化过程中扮演着至关重要的角色。对应着带电粒子在地磁场中的三种周期运动，波粒相互作用也有着三种基本共振机制：回旋共振、弹跳共振和漂移共振。其中，磁层波动与辐射带电子的回旋共振和漂移共振已经得到了较为深入的研究，而弹跳共振得到的关注却不多。研究发现，低频嘶声和电磁离子回旋波均能与辐射带电子发生弹跳共振相互作用，从而对高投掷角电子造成很强的投掷角散射。然而其对电子的能量散射以及两种波动的联合散射效应却没得到进一步的量化。本项目将从弹跳共振线性理论入手，综合考虑低频嘶声和电磁离子回旋波对电子的投掷角和能量散射以及两种波动的联合散射过程，并结合试验粒子方法探究线性理论的适用范围。通过将弹跳共振机制带入现有的辐射带数值模型之中，进一步研究低频嘶声和电磁离子回旋波弹跳共振散射电子的协同效应和各自贡献，衡量弹跳共振机制对辐射带电子动力学的影响。

波粒共振相互作用在地球辐射带电子的动力学过程中扮演着非常重要的角色。其中，等离子体层嘶声和电磁离子回旋(EMIC)波对电子的共振散射是导致辐射带电子损失的重要机制。通过结合卫星观测、理论分析和数值建模，本项目详细研究了嘶声和电磁离子回旋波对辐射带电子的共振散射效应及其对辐射带电子动力学演化过程的影响。主要研究成果包括：（1）研究了嘶声与槽区高能电子的弹跳共振相互作用，发现弹跳共振可以造成电子在高投掷角处的投掷角扩散，且高能电子的散射效应远强于低能电子；（2）评估了嘶声的冷等离子体色散关系在研究其对辐射带电子的散射损失时的有效性，发现冷等离子体近似明显低估了嘶声对低能电子的散射效应，证实了考虑热等离子体效应的必要性；（3）发现槽区嘶声的功率谱强度会随着亚暴活动的增强和L-shell的增加而显著增强，并在此基础上建立了嘶声作用下的槽区高能电子损失时间尺度的经验模型；（4）研究了极化反转过程对EMIC波共振散射辐射带电子的影响及其对L-shell、电子数密度和波动频谱的依赖性，发现极化反转显著增强了氢频段EMIC波对相对论电子的散射损失；（5）研究了低频合声波与辐射带电子的弹跳共振过程，发现弹跳共振可以造成90度附近投掷角电子的投掷角散射，并进一步对比了其与回旋共振和朗道共振之间的差异。