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

该项目将结合磁流体动力学（MHD）模拟磁暴和单个粒子追踪来研究太阳风离子在风暴时间进入磁层的情况。它将确定粒子在穿越磁层顶时是如何加速的，并将研究这些太阳风粒子作为内磁层的种子种群所起的作用。将解决的具体问题包括：太阳风质子对风暴时磁层的贡献是什么？太阳风压力脉冲对磁层的压缩是否有助于或阻碍太阳风离子进入磁层？由强烈的风暴时电流片造成的拉伸磁力线，会导致等离子体片内离子的非绝热运动吗？这个动议的结果是什么？离子进入磁层顶的过程和磁层顶重联区域的离子加速在风暴和平静时期有何不同？该研究将使用粒子轨迹计算来跟踪从MHD模拟太阳风和磁层获得的全球随时间变化的电场和磁场中的离子。粒子将被追踪到太阳风的发射点，弓形激波的上游。这些粒子将跟随它们穿过磁层顶电流层，进入磁层。在此过程中，将有可能确定进入位置和加速机制，并确定太阳风离子进入内部磁层的过程。粒子追踪技术在安静时期太阳风进入方面取得了重要的新成果。所描述的工作是先前工作的自然延伸，并将支持在安静时间和磁暴期间运行的进入机制之间的比较。该研究将使用四种特定的磁暴。这些风暴的选择包括磁性云、流-流相互作用和具有显著压力脉冲的大风暴，因此可以比较不同风暴和多个风暴阶段的粒子进入特征。不同类型风暴的结果比较也将揭示离子数量和加速机制的差异。这项研究有望为确定和预测内磁层中高能粒子的出现这一难题做出重大贡献，并有助于减轻这些粒子对天基系统和宇航员造成的空间天气危害。

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.