Global Storm-Time Losses and Radial Transport of the Outer Belt Electrons at Earth

在磁暴期间，外辐射带的相对论电子通量表现出高度的动态行为。控制电子通量变化的两个基本过程是电子穿过其漂移壳层的径向传输和由于暴时环电流引起的磁场的大规模重新配置。该项目将解决以下科学问题：（1）风暴时环电流产生的磁场扭曲和感应电场对辐射带电子总数的全球损失有何作用？(2)太阳风动压波动引起的超低频振荡如何影响外电子带的全球结构？该研究是基于一系列受控的电子输运和损失的数值实验。它使用了一个3D的测试粒子模型，提供了一个动力学描述的全球演化的辐射带的指导中心近似。该模型的以下特征对于解决全球机制的作用特别重要：（1）它基于具有感应电场的Tsyganenko-Sitnov磁场模型。该模型考虑了在磁暴主相期间内磁层场的真实动态重配置，这种重配置可产生快速的电子损失：（2）它包括了由太阳风动力学变化直接引起的超低频波动;（3）它将使用一个新开发的模型，解决三维漂移-反弹电子运动，并因此占的功能，如漂移壳分裂和轨道分叉，这是不描述的二维模型。该项目将确定在太阳风和地磁条件的作用下，热带风暴时变期间绝热反应和永久损失的相对贡献;（2）它将量化热带风暴恢复阶段的绝热程度;（3）它将确定在何处以及在何种条件下可以将外带的径向输送描述为径向扩散;以及（4）它将量化作为太阳风和地磁条件的函数的平均输运率。拟议项目的主要目标是了解地球辐射带的全球变化。 这与可能对航天器和宇航员造成危险的空间天气和现象有很大关系。在这项研究中得出的平均径向传输率将提供给建模社区使用的扩散和数据同化模型的外部bet电子通量。这项工作还将通过暑期实习生计划为学生暑期实习生提供研究培训。

During geomagnetic storms relativistic electron fluxes of the outer radiation belt exhibit highly dynamic behavior. The two basic processes controlling the variability of electron fluxes are radial transport of electrons across their drift shells and large-scale reconfigurations of the magnetic field due to the storm-time ring current. This project will address the following science questions: (1) What is the role of magnetic field distortions and inductive electric fields produced by the storm-time ring current on the global loss of radiation belt electron populations? (2) How do ULF oscillations induced by fluctuations of the solar wind dynamic pressure influence the global structure of the outer electron belt? The research is based on a series of controlled numerical experiments of electron transport and losses. It uses a 3D test-particle model which provides a kinetic description of global evolution of the radiation belt in the guiding-center approximation. The following features of the model are especially important for addressing the role of global mechanisms: (1) it is based on the Tsyganenko-Sitnov magnetic field model with inductive electric fields. The model accounts for realistic dynamic reconfigurations of the inner magnetospheric fields which can produce rapid electron losses during storm main phase; (2) it includes ULF fluctuations that are directly induced by variations in the solar wind dynamic; (3) it will use a newly developed model that resolves the three dimensional drift-bounce electron motion and therefore accounts for the features such as the drift shell splitting and orbit bifurcations, which are not described by two dimensional models. The project will determine the relative contributions of the adiabatic response and permanent losses during storm-time variability of the belt as a function of the solar wind and geomagnetic conditions; (2) it will quantify the degree of adiabaticity of the belt during storm recovery phase; (3) it will determine where and under what conditions radial transport in the outer belt can be described as radial diffusion; and (4) it will quantify the average transport rates as a function of the solar wind and geomagnetic conditions. The primary goal of the proposed project is to understand global variability of Earth's radiation belt. This has great relevance to space weather and phenomena that can create hazards for spacecraft and astronauts. The average radial transport rates derived in this study will be provided for the modeling community to use in diffusion and data-assimilation models of the outer bet electron fluxes. The work will also provide research training for student summer interns via a summer intern program.