GEM: Quantifying the Role of Radial Diffusion on the Energy-dependent Acceleration of Ultrarelativistic Electrons in the Center of Outer Radiation Belt

GEM：量化径向扩散对外辐射带中心超相对论电子依赖能量的加速的作用

• 批准号: 1952903
• 负责人: Hong Zhao
• 金额: $ 34.73万
• 依托单位: University of Colorado at Boulder
• 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: 2020-03-01 至 2021-09-30
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=1952903&HistoricalAwards=false
• 关键词: GEM; Quantifying; Role; Radial; Diffusion

In the radiation belts surrounding the Earth, electrons are accelerated to ultrarelativistic speeds. How this process occurs is a fundamental unanswered question. The project addresses the relative importance of two main acceleration mechanisms, inward radial diffusion and local acceleration. Using a novel approach to calculate the radial diffusion coefficients, this study will quantify the contribution from radial diffusion to ultrarelativisitic electron acceleration and its dependence on electron energy. The results of this project will contribute to updating space weather forecast models, which is a priority set out in the National Space Weather Action Plan. An early career researcher and an undergraduate student will receive support.This project uses a novel approach to calculate event-specific radial diffusion coefficients and quantify the role of radial diffusion in ultrarelativistic electron acceleration in the center of the outer radiation belt (L~3 – 6). Using observations of electron flux oscillations and electric/magnetic fields, combined with particle-tracing simulations, the radial diffusion coefficients will be calculated from the radial displacement of the traced particles during selected events. Combining with the radial diffusion model using the Fokker-Planck equation, the contribution of radial diffusion in the ultrarelativistic electron acceleration will be quantified, and its dependence on electron energy will be revealed. Specifically, the following science questions will be answered: (i.) How often do the ultrarelativistic electron periodic flux oscillations occur and what are the associated radial diffusion coefficients for ultrarelativistic electrons with different energies? (ii.) For selected electron flux enhancement events, quantitatively, what is the role of radial diffusion to the ultrarelativistic electron acceleration in the center of outer belt (L~3 – 6)? (iii.) How does the relative contribution of radial diffusion to the ultrarelativistic electron acceleration in the center of outer belt vary with electron energy?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.

在地球周围的辐射带中，电子设备被加速至超媒体速度。这个过程如何发生是一个基本的未解决问题。该项目解决了两种主要加速机制的相对重要性：内向径向扩散和局部加速度。使用一种新的方法来计算径向扩散系数，本研究将量化径向扩散到超层压电子加速度的贡献及其对电子能量的依赖性。该项目的结果将有助于更新太空天气预报模型，这是国家太空天气行动计划中提出的优先级。早期的职业研究员和本科生将获得支持。该项目使用一种新的方法来计算事件特异性的径向扩散系数，并量化了径向扩散在外部辐射带中心中超层流性电子加速度中的作用（L〜3 - 6）。使用电子通量振荡和电气/磁场的观察，结合粒子跟踪模拟，将根据所选事件期间的径向径向位移来计算径向差异系数。将使用Fokker-Planck方程与径向扩散模型结合，将量化径向扩散在超层压电子加速度中的贡献，并将揭示其对电子能量的依赖性。具体而言，将回答以下科学问题：（i。）超偏移性电子周期通量振荡的频率发生，并且具有不同能量的超级层压电子设备的相关径向差异是什么？ （ii。）对于选定的电子通量增强事件，量词，径向扩散到外带中心的超层流电子加速度的作用是什么（L〜3 - 6）？ （iii。）径向差异对外带中心的超偏移电子加速度的相对贡献如何随着电子能量而变化？该奖项反映了NSF的法定任务，并被认为是通过基金会的智力优点和更广泛影响的审查标准通过评估来评估的支持。

项目成果

Van Allen Probes Observations of Multi‐MeV Electron Drift‐Periodic Flux Oscillations in Earth's Outer Radiation Belt During the March 2017 Event

• DOI: 10.1029/2021ja029284
• 发表时间: 2021-07
• 期刊: Journal of Geophysical Research: Space Physics
• 作者: Hong Zhao;T. Sarris;Xinlin Li;Max Weiner;Isabela Huckabee;D. Baker;A. Jaynes;S. Kanekal;S. Elkington;M. Barani;W. Tu;Wenlong Liu;Dianjun Zhang;M. Hartinger

On the Association Between Electron Flux Oscillations and Local Phase Space Density Gradients

• DOI: 10.1029/2020ja028891
• 发表时间: 2021-02
• 期刊: Journal of Geophysical Research: Space Physics
• 作者: T. Sarris;Xinlin Li;Hong Zhao;L. Khoo;Wenlong Liu;M. Temerin