Collaborative Research: Self-Consistent Ring-Current Particle Transport Simulations

该项目旨在了解磁暴期间地球环电流的动态，并了解其对内部磁层(IM)磁场结构的影响。虽然众所周知，环电流的形成会导致内磁层出现大的磁场凹陷，但对磁暴期间IM磁场结构的全球变化还没有足够全面的了解。这样的理解是非常必要的，因为IM磁场影响IM粒子的传输、通电和损耗。实现这一目标的方法是对风暴事件应用磁场和静电自洽的环流模拟，并将模拟结果与卫星仪器(如CAMMICE和MFE仪器)的现场粒子测量结果和来自图像航天器的高能中性原子(ENA)图像的ENA图像进行比较。该项目将具体讨论(A)不同地磁风暴的环流及其磁特征的空间和时间变化，(B)环电流的不对称性以及ASY-H指数表征这种不对称性的程度，(C)环电流对DST磁指数的实际贡献，(D)感应电场在主要阶段减轻环流粒子带电的程度，并(如果有的话)延长磁暴的恢复阶段；(E)考虑到磁层等离子体压力和电离层电导(包括沉淀电子的影响)对粒子传输和损失的影响，得出自洽静电场的影响。作为这项研究的一部分，将评估基于自洽模拟的环电流动力学模型能否很好地解释等离子体压力和电流密度分布(从离子通量测量推断)以及测量的磁场和电场强度。除了模拟风暴事件外，还将进行数值实验来阐明物理过程。环电流磁场的模拟和模拟/数据比较将有助于指导全社会努力开发研究和空间气象应用所急需的更真实的内部磁层磁场模型。

This project seeks to understand the dynamics of the Earth's ring current during magnetic storms and to understand its effects on the inner magnetospheric (IM) magnetic field structure. While it is well known that the formation of a ring current leads to large magnetic field depressions in the inner magnetosphere, there is not yet a sufficient comprehensive understanding of global variations in IM magnetic field structure during magnetic storms. Such an understanding is critically needed because the IM magnetic field affects IM particle transport, energization, and loss. The approach toward this objective is to apply magnetically and electrostatically self-consistent kinetic ring current simulations for storm events and to compare the simulation results with in-situ particle measurements from satellite instruments such as the CAMMICE and MFE instruments on and energetic neutral atom(ENA) images ENA images from the IMAGE spacecraft.The project will specifically address (a) the spatial and temporal variation of the ring current and its magnetic signature for different geomagnetic storms, (b) the asymmetry of the ring current and how well the ASY-H index characterizes such asymmetries, (c) the actual contribution of the ring current to the Dst magnetic index, (d) the amount that induced electric fields mitigate the energization of ring current particles during the main phase and (if at all) prolong the recovery phase of a magnetic storm, and (e) the effects of self-consistent electrostatic fields, by taking account of magnetospheric plasma pressure and ionospheric conductances (including effects of precipitating electrons) on particle transport and loss. As part of this research, an assessment of how well self-consistent simulation-based kinetic models of the ring current can account for plasma pressure and current density distributions (inferred from ion-flux measurements) and measured magnetic and electric intensities will be made. In addition to simulating storm events, numerical experiments will be made to elucidate the physical processes. The simulations and simulation/data comparisons of the ring-current magnetic field will help guide community-wide efforts toward developing more realistic models of the inner magnetospheric magnetic field that are critically needed for research and space weather applications.