GEM: The Dynamics of Solar Wind Ion Entry into the Magnetosphere during Magnetic Storms

该项目将结合磁暴的磁流体动力学(MHD)模拟和单个粒子追踪来研究太阳风离子在风暴期间进入磁层的情况。它将确定粒子在穿过磁层顶时如何加速，并将调查这些太阳风粒子作为内部磁层的种子种群所起的作用。将讨论的具体问题包括：太阳风质子对风暴时期的磁层有什么贡献？太阳风压力脉冲对磁层的压缩是有助于还是阻碍太阳风离子进入磁层？强风暴时电流片产生的拉伸磁力线是否会导致等离子体片内离子的非绝热运动？这项议案的后果是甚麽？在风暴和平静时期，离子通过磁层顶进入和磁层顶重联区域的离子加速过程有何不同？这项研究将使用粒子轨迹计算来跟踪全球随时间变化的电场和磁场中的离子，这些电场和磁场是通过MHD对太阳风和磁层的模拟获得的。粒子将从太阳风中的发射点被追踪，在弓形激波的上游。粒子将穿过磁层顶电流层，进入磁层。在这一过程中，将有可能确定进入地点和加速机制，并确定太阳风离子进入内磁层的过程。将要使用的粒子示踪技术已经为太阳风在安静时期进入太阳产生了重要的新结果。所描述的工作是先前工作的自然扩展，并将支持在安静时间和磁暴期间工作的进入机制之间的比较。研究中将使用四种特定的磁暴。选择这些风暴包括磁云、流-流相互作用和具有显著压力脉冲的大型风暴，从而可以比较不同风暴和多个风暴阶段的粒子进入特性。对不同类型风暴的结果的比较也将揭示离子群和加速机制的差异。这项研究有望为确定和预测高能粒子在内部磁层中的出现作出重大贡献，并将有助于减轻这些粒子对天基系统和宇航员造成的空间气象危害。

This project will use a combination of magnetohydrodynamic (MHD) simulations of magnetic storms and individual particle tracing to investigate the storm-time entry of solar wind ions into the magnetosphere. It will determine how particles are accelerated as they cross the magnetopause, and will investigate what role these solar-wind particles play as a seed population for the inner magnetosphere. The specific questions that will be addressed include: What contributions do solar wind protons make to the storm-time magnetosphere? Does the compression of the magnetosphere by solar wind pressure pulses assist or hinder the entry of solar wind ions into the magnetosphere? Do stretched magnetic field lines, resulting from intense storm-time current sheets, lead to the nonadiabatic motion of ions within the plasma sheet? What are the consequences of this motion? How do the processes of ion entry through the magnetopause and ion acceleration in the magnetopause reconnection regions differ during storms and during quiet times? The research will use particle trajectory calculations to follow ions in global time-dependent electric and magnetic fields obtained from MHD simulations of the solar wind and magnetosphere. Particles will be traced from launch points in the solar wind, upstream of the bow shock. The particles will be followed through the magnetopause current layer, and into the magnetosphere. In the process it will be possible to identify entry locations and acceleration mechanisms, and identify the processes whereby solar wind ions gain access to the inner magnetosphere. The particle tracing technique to be used has yielded significant new results for solar wind entry during quiet times. The work described is a natural extension of that previous work and will support comparisons between entry mechanisms operating during quiet times and during magnetic storms.Four specific magnetic storms will be used in the study. These storms are chosen to include magnetic clouds, stream-stream interactions, and large storms with significant pressure pulses, and thus will allow comparison of particle entry characteristics of the different storms and the multiple storm phases. The comparison of results for different types of storms will also shed light on differences in ion populations and acceleration mechanisms. The study promises to provide a significant contribution to the puzzle of determining and forecasting the occurrence of high-energy particles in the inner magnetosphere and will help mitigate the space weather hazards caused by these particles on space-based systems and on astronauts.