GEM: Quantitative Comparison of the Theory and Observations of Relativistic Electron Precipitation due to Electromagnetic Ion Cyclotron Waves

GEM：电磁离子回旋波引起的相对论性电子沉淀的理论与观测的定量比较

• 批准号: 0503371
• 负责人: Robyn Millan
• 金额: $ 27.42万
• 依托单位: Dartmouth College
• 依托单位国家: 美国
• 项目类别: Continuing Grant
• 财政年份: 2005
• 资助国家: 美国
• 起止时间: 2005-05-15 至 2009-04-30
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=0503371&HistoricalAwards=false
• 关键词: GEM; Quantitative; Comparison; Theory; Observations

Attaining a quantitative understanding of relativistic electron variability in the radiation belts is an important scientific issue. Quantifying and understanding electron losses is now recognized as an integral part of understanding this variability; the trapped flux depends on a delicate balance between sources and losses. Substantial progress has recently been made in modeling acceleration processes, but including losses in these models will be necessary ultimately. Specifically, it must be determined under what conditions local acceleration dominates over radial diffusion, and whether either of these models is capable of explaining relativistic electron enhancements in the presence of the strong losses that have been demonstrated. One of the major loss mechanisms that has been proposed is pitch-angle scattering by electromagnetic ion cyclotron waves. The project will use a hybrid simulation code (fluid electrons and kinetic particle ions) to perform a theoretical study of relativistic electron precipitation due to electromagnetic ion cyclotron waves. Data from geosynchronous satellites and the IMAGE spacecraft will be used to determine EMIC wave growth rates under specific geomagnetic conditions. The interaction of relativistic electrons with the waves will be studied by using the electrons as test particles in the simulated waves. The study will determine under what conditions EMIC waves grow, and will determine the pitch angle scattering rate of electrons as a function of energy. It will also determine the effect of ULF waves on EMIC wave amplitude and electron precipitation. Results from the test particle simulation will be quantitatively compared with observations of precipitation from three balloon campaigns. Specifically, we will determine if EMIC waves can explain features of the observed precipitation, such as the energy spectrum, flux, local time, and temporal structure, given the geomagnetic conditions observed during each precipitation event. Two graduate students will be involved in the research. The project will benefit society by working towards a predictive capability of space weather effects of the radiation belts.

在辐射带中对相对论电子变异性的定量了解是一个重要的科学问题。量化和理解电子损失现在被认为是理解这种变异性的组成部分；捕获的通量取决于来源和损失之间的微妙平衡。最近在建模加速过程中取得了重大进展，但最终将需要在这些模型中包括损失。具体而言，必须在径向扩散统治的情况下确定局部加速度在什么条件下确定，以及这些模型中的任何一个是否能够在存在已证明的强损失的情况下解释相对论电子的增强。提出的主要损失机制之一是电磁离子回旋体波散射螺距角。该项目将使用混合模拟代码（流体电子和动力学颗粒离子）来对电磁离子环旋巨波引起的相对论电子沉淀进行理论研究。地球同步卫星和图像航天器的数据将用于确定特定地磁条件下的EMIC波生长速率。相对论电子与波浪的相互作用将通过使用电子作为模拟波中的测试粒子进行研究。该研究将确定在什么条件下，EMIC波的生长，并将确定电子的俯仰角散射速率随能量的函数。它还将确定ULF波对EMIC波幅度和电子沉淀的影响。与三个气球运动的降水观察结果相比，测试粒子模拟的结果将进行定量。具体而言，我们将确定emic波是否可以解释观察到的降水的特征，例如能量光谱，通量，局部时间和时间结构，鉴于每个降水事件中观察到的地磁条件。两名研究生将参与研究。该项目将通过致力于辐射带的太空天气影响的预测能力来使社会受益。