低频电磁波驱动的地球辐射带能量电子蝴蝶型分布恢复过程

Pitch-angle is an essential parameter that controls movement of charged particles in magnetic field and plays a key role in the eletron acceleration, loss and transport processes in the Earth's magnetosphere. Energetic electrons in the Earth's radiation belts pose a serious threat to the orbiting satellites and astronauts. Investigation of pitch-angle distributions (PADs) of electrons helps to understand the dynamic evolution of radiation belts electron flux. Electron PAD present different patterns in the radiation belts and butterfly distribution is one of the most common distributions. Formation of butterfly PAD has received much attention in the past several years and many studies have been performed to investigate it. However, relatively few works have been done to research the recovery process from butterfly PAD to other PADs. Interaction between radiation belt electrons and low frequency electronmagnetic waves is regarded as a potential mechanism for butterfly PAD recovery according to recent research works. This project aims to conduct a comprehensive and in-depth research on the recovery process of butterfly PADs driven by multi-mode low frequency electromagnetic waves. In this proposal, we intend to incorporate satellite data treatment, theoretical research and numerical simulation. We shall study the spatial distribution，instability and propagation of different mode waves. We plan to perform a systematic analysis on the scattering in energy and pitch angle of energetic electrons via gyroresonant interaction, solve the Fokker-Planck diffusion equation and study the PAD evolution induced by low frequency electromagnetic waves.

投掷角是控制带电粒子在磁场中运动的一个基本参数，它对地球磁层中电子的加速、损失和输运过程有着关键影响。地球辐射带中的能量电子对在轨航天器和航天员的安全构成严重威胁，研究投掷角分布有助于了解电子通量的动力学演化。辐射带中电子投掷角分布有多种形态，蝴蝶型分布是其中一种常见类型。电子蝴蝶型分布的形成在过去受到了很多关注并进行了一些研究，而相反的过程即恢复过程当前研究甚少。最近的研究表明，低频电磁波与电子的相互作用是蝴蝶型分布恢复的一种可能机制。本项目旨在针对多种波模低频电磁波在电子蝴蝶型分布恢复过程中的作用进行全面深入的研究。计划结合卫星数据分析、理论研究和数值模拟，研究不同波模电磁波的传播特性，不稳定性以及空间分布，系统分析低频电磁波与电子的回旋共振作用特征，求解Fokker-Planck动力学方程，研究低频电磁波驱动下电子投掷角分布的演化。

本项目对电子蝴蝶型投掷角分布的恢复过程进行了全面深入的研究，结合卫星数据分析、理论研究和数值模拟，系统地分析了低频电磁波与辐射带电子的共振相互作用，研究了电磁波驱动下能量电子投掷角分布的演化。我们的研究表明哨声模合声波与电子的共振作用是造成蝴蝶型投掷角分布恢复的一种有效物理机制。此外，我们还结合数值模拟和数据统计等手段，探讨了辐射带区域多种低频电磁波（哨声模合声波、闪电激发哨声波、电磁离子回旋波、静电回旋波、极光千米波等）的激发机制，研究了低频电磁波的波谱特征，探讨了它们在磁层中的传播特性，统计了它们在时间上的演化和空间上的分布规律。我们的研究深化了对于辐射带低频电磁波统计规律的认识，有助于进一步理解辐射带的动力学演化。