GEM: Applications of a Modular Open Magnetosphere Model

拟议的工作将应用现有的开放磁层模块模型来解决对NSF地球空间建模计划至关重要的三个问题。提出的工作目标是发展对(1)太阳风等离子体通过日侧磁层尖端注入的预测性理解，(2)外部或内部施加的极帽结构的时间变化，以及(3)由近北行星际磁场（IMF）驱动的反向对流。该方法将物理数值模拟与航天器数据分析相结合。该模型是在过去十年中在GEM项目的部分支持下发展起来的，它描述了从磁层顶到极地电离层沿相互连接的磁力线的太阳风电场的定量映射。该模型的一个机器便携、用户友好的稳态应用版本最近已提供给GEM研究界。最近对该模型的扩展允许放宽对依赖时间的应用的稳态假设。第一个应用是尖离子注入的建模，涉及到与T. Onsager正在进行的合作，将他的Liouville绘图程序与模块化开放磁层模型结合起来，产生定量的真实的尖离子分布模拟，以便与实际的航天器数据进行比较，用于输入太阳风/IMF条件的一般范围。本研究旨在阐明太阳风等离子体在日侧磁层顶注入形成尖端和邻近边界特征的机制。第二个应用程序将探索两种类型的极帽准静态时间演化，一种是由太阳风/IMF变化驱动的外部时间演化，另一种是由磁尾动力学驱动的内部时间演化，磁尾动力学通过从磁尾合并线绘制的电场传递给电离层。这项研究将利用极帽的独特性质，不仅作为观测地点，而且作为理论数值模拟的参考框架。第三个申请将继续与N.U. Crooker合作，开发一个由她提出的覆盖瓣结构的定量模型，以解释在几乎向北的IMF间隔期间与太阳风相连的推定开放瓣场线上的向太阳对流的其他神秘观测。这和相关的北向imf现象可能代表了目前对太阳风-磁层耦合理论认识中最大的差距。

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.