GEM: From the Micro to the Macro--Identifying the Mechanisms Responsible for Megaelectron-Volt (MeV) Electron Microbursts and Quantifying Their Role in Global Radiation Belt Losses

GEM：从微观到宏观——确定兆电子伏（MeV）电子微爆发的机制并量化其在全球辐射带损失中的作用

• 批准号: 2025706
• 负责人: Jacob Bortnik
• 金额: $ 39.74万
• 依托单位: University of California-Los Angeles
• 依托单位国家: 美国
• 项目类别: Standard Grant
• 财政年份: 2020
• 资助国家: 美国
• 起止时间: 2020-09-01 至 2024-08-31
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=2025706&HistoricalAwards=false
• 关键词: GEM; Micro; Macro; Identifying; Mechanisms

The dynamical evolution of the Earth’s radiation belts is governed by the relative balance between particles being accelerated and transported into and lost from the magnetosphere. Relativistic electron microbursts are one source of particle losses in the magnetosphere. This work is a modeling effort to better understand the physical process of losses from microbursts. The work will have a broader impact on the technological infrastructure that supports our society and national security, due to the significant space weather hazard that radiation belt electrons pose to Earth-orbiting spacecraft. Two undergraduates and one graduate student researcher will be supported.The effort will develop a computational framework to identify the physical mechanisms that produce relativistic electron microbursts in the Earth’s outer radiation belt and to quantify, for the first time, accurate loss estimates due to this scattering process. The science investigation will be carried out as follows. Numerical ray tracing will be used to calculate the chorus wave power spectrum (frequency and wave normal angle) as a function of time and location along a given magnetic field line, including Landau damping. Then, the wave power distribution will be used to calculate the resultant pitch-angle change near the loss cone at each point along the field line due to resonant interactions with the obtained chorus wave field, including nonlinear effects. This is then repeated for a set of test-particles (i.e., energetic electrons) over a range of initial energies. For an assumed radiation belt electron distribution taken from an empirical model, the work calculates the spatio-temporal dependence of the electron flux precipitated into the ionosphere due to the derived resonant pitch-angle scattering. Repeating this entire procedure across a range of locations provides a map of the electron flux precipitated into the ionosphere as a function of time, position, and energy, due to resonant interactions with chorus waves. With these model calculations in hand, the work explores and evaluates the various potential mechanisms involved in the scattering through parameter variation, for example by increasing/suppressing Landau damping, or by restricting/including higher order resonances. These mechanisms will then be additionally scrutinized through data-model comparisons, both statistical and for an individual event.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.

地球辐射带的动态演化受颗粒加速并从磁层中输入和流失的颗粒之间的相对平衡。相对论电子微果是磁层中粒子损失的一种来源。这项工作是一项建模工作，以更好地了解微生物损失的物理过程。这项工作将对支持我们社会和国家安全的技术基础设施产生更大的影响，这是因为辐射带电子对地球轨道航天器的巨大危险危害。将支持两名大学生和一名研究生研究人员。这项工作将开发一个计算框架，以确定在地球外辐射带中产生相对主义的电子微事物的物理机制，并首次量化由于这种散射过程，因此首次量化了准确的损失估计。科学调查将如下进行。数值射线跟踪将用于计算合唱波功率谱（频率和波正正角），作为沿特定磁场线（包括Landau阻尼）的时间和位置的函数。然后，由于与获得的合唱波场的共振相互作用，包括非线性效应，波浪发电机分布将用于计算每个点附近的损耗锥附近的螺距角变化。然后，在一系列初始能量范围内重复一组测试粒子（即能量电子）。对于从经验模型中获取的假定辐射带电子分布，该工作计算出由于衍生的谐振螺距散射而导致的电子通量的时空依赖性。在各个位置重复整个过程，提供了由于与合唱波的共振相互作用而导致的时间，位置和能量的函数，这些电子通量的图是电离层中规定的电子通量图。通过手头上的这些模型计算，该作品可以通过参数变化探索和评估散射中涉及的各种潜在机制，例如，通过增加/抑制Landau阻尼或限制/包括高阶共振来限制/抑制/抑制。然后，这些机制将通过统计和个人事件进行数据模型比较进行仔细检查。该奖项反映了NSF的法定任务，并使用基金会的知识分子优点和更广泛的影响评估标准，认为通过评估值得一提。

项目成果

Structure of Energy Precipitation Induced by Superbolt‐Lightning Generated Whistler Waves

超级闪电——闪电产生的惠斯勒波引起的能量沉淀的结构

• DOI: 10.1029/2022gl097770
• 发表时间: 2022
• 期刊: Geophysical Research Letters
• 影响因子: 5.2
• 作者: Kang, Ning;Bortnik, Jacob
• 通讯作者: Bortnik, Jacob

Propagation of Chorus Waves Generated in Minimum‐B Pockets

• DOI: 10.1029/2021gl096478
• 发表时间: 2021-12
• 期刊: Geophysical Research Letters
• 影响因子: 5.2
• 作者: N. Kang;J. Bortnik;X. An;S. Claudepierre