Collaborative Research: GEM--The Upper Limit of the Earth's Outer Radiation Belt Electron Fluxes

地球的外辐射带电子，也被称为“杀手电子”，可能会对地球轨道卫星和我们史无前例的依赖天基连接的社会构成重大危险。这些电子的主要加速机制包括向内的径向扩散和局域波粒子与哨声模式合唱波的相互作用。最近的研究表明，这些电子的流量接近上限，这并不一定取决于地磁风暴的大小。然而，控制外辐射带电子通量上限的关键地磁条件和潜在的物理机制仍然未知。评估和预测地球外辐射带中这些电子通量的极端情况，不仅对空间科学界，而且对空间工业和经济都很重要。这项提议旨在揭开驱动因素，并构建一个地磁活跃时期地球外辐射带电子通量上限的预测模型。PI是一位职业生涯早期的女科学家，将由一名资深教职员工指导。这项提议的主要目标是调查地球辐射带电子通量的上限。将回答的科学问题包括：(1)利用统计分析和机器学习技术，什么是临界地磁条件，以及各种地磁指数对地球外辐射带观测到的通量上限的定量贡献？(2)准线性扩散模拟中的关键输入参数(如波参数、总电子密度、径向扩散、(3)用拟线性理论对哨声模式合唱波的局部加热引起的通量上限的分析估计是什么，它们与卫星观测观测到的通量上限有什么关系？为了解决这些问题，该团队将结合使用NASA范艾伦探测器的测量结果的统计卫星数据分析、数值建模，以及使用准线性机制和机器学习技术的分析方法，以确定导致通量上限的关键因素，并开发最大外带电子通量的预测模型。该项目的结果将提供关于风暴和亚风暴活动对辐射带电子通量的累积影响的见解，以及加速的物理驱动因素，并为建立外辐射带最大电子通量预测模型而发展必要的理解。我们的提案将有一个次要目标，即探索我们如何学习使用机器学习模型来进行科学洞察发现。该奖项反映了NSF的法定使命，并通过使用基金会的智力优势和更广泛的影响审查标准进行评估，被认为值得支持。

The Earth’s outer radiation belt electrons, also known as “killer electrons”, can pose a significant hazard to Earth-orbiting satellites and our unprecedented space-based connection-dependent society. The major acceleration mechanisms for these electrons include inward radial diffusion and local-wave particle interactions with whistler-mode chorus waves. Recent studies have demonstrated the approach of an upper limit of the fluxes of these electrons, which does not necessarily depend on the magnitude of the geomagnetic storm. However, the critical geomagnetic conditions and the underlying physical mechanisms that control this upper limit of the outer radiation belt electron fluxes still remain unknown. Assessing and forecasting the extreme case of these electron fluxes in the Earth’s outer radiation belt is important not only to the space science community but also to the space industry and economy. This proposal aims to unravel the driver and construct a prediction model for the upper limit of the Earth’s outer radiation belt electron fluxes during geomagnetically active times. The PI is an early-career female scientist and will be mentored by a senior faculty. The primary objective of this proposal is to investigate the upper limit of the Earth’s radiation belt electron fluxes. The science questions that will be answered include: (1) What are the critical geomagnetic conditions and the quantitative contributions of various geomagnetic indices to the observed flux upper limits in the Earth’s outer radiation belt using both statistical analysis and machine learning techniques? (2) What are the key input parameters in the quasi-linear diffusion simulation (e.g., wave parameters, total electron density, radial diffusion, background magnetic field) that produce higher flux upper limits driven by chorus waves? (3) What is the analytical estimate of the upper limits of fluxes that are due to local heating by whistler-mode chorus waves using quasi-linear theory and what are their correlations with the observed flux upper limits from satellite observations? To address these questions, the team will combine statistical satellite data analysis using measurements from NASA’s Van Allen Probes, numerical modeling, and an analytical approach using the quasi-linear regime and machine learning technique to identify the key factors that contribute to creating the upper limit of fluxes, and develop predictive models of the maximum outer belt electrons fluxes. The results of this project will provide insights regarding the cumulative impacts of storm and substorm activity on the radiation belt electron fluxes, the physical drivers of acceleration, and develop the necessary understanding to produce forecasting models of maximum electron fluxes in the outer radiation belt. Our proposal will have a secondary goal of exploring how we can learn to use machine learning models for scientific insight discovery.This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.