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

合作研究：GEM--地球外辐射带电子通量上限

• 批准号: 2247255
• 负责人: Man Hua
• 金额: $ 37.6万
• 依托单位: University of California-Los Angeles
• 依托单位国家: 美国
• 项目类别: Continuing Grant
• 财政年份: 2023
• 资助国家: 美国
• 起止时间: 2023-09-01 至 2026-08-31
• 项目状态: 未结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=2247255&HistoricalAwards=false
• 关键词: Collaborative; Research; GEM; Upper; Limit

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.

地球外辐射带电子，也称为“杀手电子”，可能对地球轨道卫星和我们前所未有的依赖太空连接的社会构成重大危害。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，这些电子的通量的上限，这并不一定取决于磁暴的大小的方法。然而，控制外辐射带电子通量上限的临界地磁条件和基本物理机制仍然未知。评估和预测地球外辐射带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。该建议旨在解开驱动因素，并构建地磁活跃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，将由一位高级教师指导。这项提议的主要目的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）使用统计分析和机器学习技术，临界地磁条件是什么以及各种地磁指数对观测到的地球外辐射带通量上限的定量贡献是什么？(2)准线性扩散模拟中的关键输入参数是什么（例如，波参数，总电子密度，径向扩散，背景磁场），产生更高的通量上限由合唱波驱动？(3)使用准线性理论对哨声模式合唱波造成的局部加热所产生的通量上限的分析估计是什么，它们与卫星观测所观测到的通量上限的相关性是什么？为了解决这些问题，该团队将联合收割机结合统计卫星数据分析，使用美国宇航局货车艾伦探测器的测量值，数值建模，以及使用准线性制度和机器学习技术的分析方法，以确定有助于创建通量上限的关键因素，并开发最大外部带电子通量的预测模型。这一项目的结果将有助于深入了解风暴和亚风暴活动对辐射带电子通量的累积影响、加速的物理驱动因素，并为制作外辐射带最大电子通量的预测模型提供必要的了解。我们的提案的第二个目标是探索如何学习使用机器学习模型进行科学洞察发现。该奖项反映了NSF的法定使命，并通过使用基金会的知识价值和更广泛的影响审查标准进行评估，被认为值得支持。