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

在地磁暴期间，外辐射带的相对论性电子通量表现出高度动态的行为。控制电子通量变异性的两个基本过程是电子在其漂移壳层上的径向输运和由风暴时环电流引起的磁场的大规模重构。该项目将解决以下科学问题：(1)风暴时环电流产生的磁场畸变和感应电场对辐射带电子种群的全球损失有何作用？(2)由太阳风动压波动引起的极低频振荡如何影响外层电子带的整体结构？该研究是基于一系列电子输运和损失的受控数值实验。它采用三维测试粒子模型，在导向中心近似下提供辐射带全局演化的动力学描述。该模型的以下特征对于解决全局机制的作用尤为重要：(1)它基于具有感应电场的Tsyganenko-Sitnov磁场模型。该模型考虑了风暴主阶段内磁层场的实际动态重构，这种重构会产生快速的电子损失；(2)包括由太阳风动力学变化直接引起的极低频波动；(3)将采用新开发的模型来解决三维漂移-弹跳电子运动，从而考虑到二维模型无法描述的漂移壳分裂和轨道分岔等特征。该项目将确定该带的绝热响应和永久损失在风暴时间变率期间作为太阳风和地磁条件的函数的相对贡献；(2)量化了风暴恢复阶段带的绝热程度；(3)决定了在什么地方和什么条件下外带的径向输运可以称为径向扩散；(4)将平均输运率量化为太阳风和地磁条件的函数。拟议项目的主要目标是了解地球辐射带的全球变异性。这与可能对航天器和宇航员造成危害的空间天气和现象有很大关系。本研究得出的平均径向输运率将提供给建模界用于外层电子通量的扩散和数据同化模型。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.