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.

对辐射带中相对论性电子变率的定量理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可变性的一个组成部分;捕获的通量取决于源和损失之间的微妙平衡。最近在模拟加速过程方面取得了实质性进展，但最终将有必要在这些模型中包括损失。具体来说，它必须确定在什么条件下局部加速主导径向扩散，以及这些模型是否能够解释相对论电子增强的存在下，已被证明的强损失。已经提出的主要损耗机制之一是电磁离子回旋波的俯仰角散射。该项目将使用混合模拟代码（流体电子和动力粒子离子）对电磁离子回旋波引起的相对论电子沉淀进行理论研究。地球同步卫星和IMAGE航天器提供的数据将用于确定特定地磁条件下EMIC波的增长率。在模拟的波中，用相对论性电子作为测试粒子，研究相对论性电子与波的相互作用。该研究将确定EMIC波在什么条件下生长，并将确定电子的俯仰角散射率作为能量的函数。还将确定ULF波对EMIC波振幅和电子沉淀的影响。试验粒子模拟的结果将与三个气球活动的降水观测结果进行定量比较。具体来说，我们将确定EMIC波是否可以解释观测到的降水特征，如能谱，通量，当地时间和时间结构，在每个降水事件期间观察到的地磁条件。两名研究生将参与这项研究。该项目将通过努力提高对辐射带空间气象影响的预测能力而造福社会。