亚暴注入对电子辐射带动态演化作用的模拟研究

The electron radiation belt consists of electrons with energies approximately from 0.1MeV to 10MeV trapped in the Earth's magnetosphere. There are two distinct radiation belts naturally separated by the slot region: relatively stable inner belt and highly variable outer belt. Observations show that the outer radiation belt electron fluxes can vary by one to three orders of magnitude on a timescale of minutes to days during the geomagnetically active times. These energetic electrons can yield serious damage to the space-borne systems and astronauts. Therefore understanding the physical mechanisms for electron radiation belt evolution and further predicating its variations has both scientific and practical significance. Based on our previous works, we shall develop an electron radiation belt kinetic model with incorporation of substorm injection, radial diffusion, local wave-particle interactions, and adiabatic transport. The effect of substorm injection on electron radiation belt evolution shall be comprehensively investigated through the combination of simulations and observations. The main objectives of this proposal are to quantify the direct contribution of a single substorm injection or a series of substorm injections to ～MeV electron flux enhancements, and the coupling effect between substorm injection and other physical processes.

电子辐射带是由捕获在地球磁场中的～0.1MeV 到10MeV 的高能电子组成的，它可以分为相对稳定的内辐射带和剧烈动态演化的外辐射带。观测结果显示，地磁活动期间，外辐射带电子通量能够在几分钟到几天时间尺度内变化一到三个数量级。这些高能电子引起的表面充电和深层充电效应严重威胁在轨卫星的正常运行。因此，理解和预报电子辐射带动力学过程具有重要的科学和实用价值。在以往研究工作的基础上,本项目将建立一个全面包含亚暴注入、径向扩散、局地波粒相互作用和绝热输运的辐射带动力学模型。结合观测数据和数值模拟深入分析亚暴注入过程对电子辐射带演化的作用，力图确定单个或者连续多个亚暴注入过程对辐射带～MeV电子通量增强事件的直接贡献，以及亚暴注入与其他物理机制耦合过程的最终效应。

本项目研究磁层亚暴活动及多种等离子体波动对辐射带电子演化的贡献。主要的研究成果如下：（1）即使在非磁暴期，亚暴活动依然能够激发强烈的合声波进而有效加速辐射带相对论电子；（2）亚暴注入激发合声波的过程不是局限于磁层子夜经晨侧至正午的空间区域，而是能够扩展至磁层昏侧区域；（3）对于相对论电子通量的增强，亚暴注入的直接贡献较小（20%），而合声波的局地加速占主导作用（80%）；（4）在不存在亚暴活动和合声波的条件下，太阳风动压扰动能够激发强烈的超低频波，进而对辐射带相对论电子进行有效加速；（5）等离子体层内部的嘶声波起源于等离子层外合身波，而不是完全由局地的不稳定性激发；（6）等离子体层外嘶声波由等离子体层内的嘶声波泄露形成的，两种嘶声波对辐射带电子具有相当的损失作用。这些研究成果对于理解辐射带复杂动力学过程以及未来的空间天气预报具有重要意义。