GEM: Applications of a Modular Open Magnetosphere Model

这项拟议的工作将把现有的开放磁层模块模型应用于对NSF地球空间建模计划至关重要的三个问题。拟议工作的目标是对(1)通过日侧磁层尖点注入太阳风等离子体，(2)极帽配置的外部或内部强加的时间变化，以及(3)由近乎向北的行星际磁场驱动的反向对流的预测了解。该方法将物理-数值模拟与航天器数据分析相结合。该模型是在GEM计划的部分支持下在过去十年中开发的，描述了沿着相互连接的磁力线从磁层顶到极地电离层的太阳风电场的定量映射。该模型的机器便携、用户友好的稳态应用版本最近已提供给创业板研究界。最近对该模型的一个扩展允许对时间依赖应用的稳态假设进行放松。第一个应用--尖点离子注入模型，涉及与T.Onsager正在进行的协作，将他的Liouville测绘程序与模块化开放磁层模型结合起来，以产生对尖点离子分布的真实定量模拟，以便与航天器在各种输入太阳风/国际货币基金组织条件下的实际数据进行比较。本研究旨在阐明(S)在日侧磁层顶注入太阳风等离子体形成尖点和相邻边界特征的机制。第二个应用将探索极帽的两种准静态时间演变，一种是由太阳风/IMF变化外部驱动的，另一种是由磁尾动力学驱动的，通过从尾部合并线映射到电离层的电场传递到电离层。这项研究将利用极冠的独特性质，不仅作为一个观察点，而且作为理论-数值模拟的参考框架。第三个应用程序将继续与N.U.Crooker合作，开发由她提出的覆盖叶结构的量化模型，以解释在IMF接近向北的间隔期间，在假定与太阳风相连的开放叶场线上观察到的向日对流的神秘观测。这一现象以及相关的向北-国际货币基金组织现象可能代表了目前对太阳-风-磁层耦合的理论理解中最大的差距。

The proposed work would apply an existing modular model of the open magnetosphere to three problems that are critical to the NSF Geospace Modeling Program. The objectives of the proposed work are to develop a predictive understanding of (1) injection of solar- wind plasma through the dayside magnetospheric cusp, (2) externally or internally imposed time variations of the polar cap configuration, and (3) reverse convection driven by a nearly northward interplanetary magnetic field (IMF). The proposed method combines physical-numerical modeling with spacecraft data analysis. The model, developed over the past decade with partial support of the GEM program, describes the quantitative mapping of the solar wind electric field from the magnetopause to the polar ionosphere along interconnected magnetic field lines. A machine-potable, user-friendly version of this model for steady-state applications has recently been made available to the GEM research community. A recent extension of this model permits relaxation of the steady- state assumption for time-dependent applications. The first application, modeling of cusp ion injection, involves an ongoing collaboration with T. Onsager to couple his Liouville mapping procedure with the modular open magnetosphere model to produce quantitatively realistic simulations of cusp ion distributions for comparison with real spacecraft data for a general range of input solar-wind/IMF conditions. This study is intended to elucidate the mechanism(s) if injection of solar-wind plasma at the dayside magnetopause to form the cusp and adjacent boundary features. The second application will explore two types of quasi-static time evolution of the polar cap, those driven externally by solar- wind/IMF variations and those driven internally by magnetotail dynamics as communicated to the ionosphere by the electric field mapped from the tail merging line. This study will exploit the unique properties of the polar cap not only as an obs ervation site but also as a reference frame for theoretical-numerical modeling. The third application will continue a collaboration with N.U. Crooker to develop a quantitative model of the overdraped lobe configuration proposed by her to explain the otherwise enigmatic observation of sunward convection on putatively open lobe field lines connected to the solar wind during intervals of nearly northward IMF. This and related northward-IMF phenomena represent perhaps the widest gap in present theoretical understanding of solar-wind-magnetosphere coupling.