Collaborative Research: GEM: Plasma Transport from the Solar Wind to the Inner Magnetosphere

该项目将研究导致太阳风离子从磁鞘传输到磁层以形成等离子体片的物理过程。因此，在不同的行星际磁场(IMF)和太阳风条件下，磁鞘、尾叶、尾翼和等离子体片中的离子分布将得到表征。这项研究将讨论太阳风离子从不同地点进入磁层的传输是否提供了形成静止和风暴时间等离子体片所需的不同能量的足够粒子。太阳风种群的变化对等离子体片中的变化的影响也将被检验。该方法将开发和使用动力学模拟来研究相关的粒子传输过程，并将模拟结果与来自GeoTail、国际太阳地球探测器(ISEE)、活动磁层粒子示踪器探测器(AMPTE)和国防气象卫星计划(DMSP)等卫星的已发表观测结果进行比较。该模型将跟踪整个粒子的运动，或者(在适当的情况下)太阳风离子从磁鞘到磁层的引导中心漂移。在磁鞘中，该模型将使用一个解析磁场，该磁场非常好地再现了从气体动力学计算中获得的磁鞘场线的形状。磁鞘电场与太阳风速度和磁场的叉积成正比。特别是对于向南移动的IMF，磁鞘的磁力线将与最初关闭的磁层磁力线重新连接。磁层模型将使用磁电自洽的莱斯对流模型(RCM-E)，其磁场边界条件包括非均匀穿透磁场的影响。这个磁层模型维持了磁层等离子体和磁场之间的内力平衡。使用RCM-E将允许计算磁层(包括尾翼和等离子体片)内的粒子通量、等离子体压力和电流密度的自洽分布。我们将研究不同太阳风条件下分布的演变，并将模拟结果与观测结果进行比较。这项工作的一个重要成果将是从物理上了解太阳风等离子体的性质(例如速度和密度)与产生的等离子体片之间的关系，而等离子体片是环电流的主要来源。这将为从太阳风特性和国际货币基金组织的条件来描述磁暴(并最终解释内部磁层中粒子数量的变化)提供一个目前缺失的环节。这一成果将有利于了解和预报空间天气，从而有利于社会。这个项目的很大一部分资金专门用于支持加州大学洛杉矶分校一名研究生的研究培训。

This project will investigate the physical processes that lead to the transport of solar wind ions from the magnetosheath and into the magnetosphere to form the plasma sheet. Ion distributions in the magnetosheath, tail lobes, tail flanks, and plasma sheet will thus be characterized for different Interplanetary Magnetic Field (IMF) and solar wind conditions. The study will address whether the transport of solar wind ions into the magnetosphere from different locations supply sufficient particles of different energies needed to form the quiescent and storm-time plasma sheet. The effect of changes in the solar wind population on the variance in the plasma sheet will also be examined. The approach will be to develop and use kinetic simulations to study the relevant particle transport processes and to compare the simulation results with published observations from satellites such from Geotail, International Sun-Earth Explorer (ISEE), Active Magnetospheric Particle Tracer Explorers (AMPTE), and Defense Meteorological Satellite Program (DMSP). The model will follow the full particle motion or (where appropriate) the guiding-center drifts of solar-wind ions from the magnetosheath into the magnetosphere. In the magnetosheath, the model will use an analytical magnetic field that reproduces quite well the shape of magnetosheath field lines obtained from gas-dynamic calculations. The magnetosheath electric field is proportional to the cross product of the solar-wind velocity and the magnetic field. Especially for southward IMF, the magnetosheath's magnetic field lines will reconnect with initially closed magnetospheric field lines. The magnetospheric model will use the magnetically and electrically self-consistent Rice Convection Model (RCM-E) with a magnetic field boundary condition that includes the effect of a non-uniform penetration magnetic field. This magnetospheric model maintains internal force balance between the magnetospheric plasma and magnetic field. Use of the RCM-E will allow the calculation of self-consistent distributions of particle flux, plasma pressure, and current density within the magnetosphere (including the tail flanks and plasma sheet). The evolution of the distributions in response to varying solar wind conditions will be studied, and the simulation results will be compared with observations. A significant outcome of this work will be a physical understanding of the relationship between properties of the solar-wind plasma (e.g., velocity and density) and the resulting plasma sheet, which is the main source for the ring current. This would provide a currently missing link for characterizing magnetic storms (and eventually accounting for variations of particle population in the inner magnetosphere) from solar-wind properties and IMF conditions. Such an achievement would be beneficial for understanding and forecasting space weather, and thus for society. A significant portion of the funds for this project are dedicated to support the research training of a UCLA graduate student.