GEM: Applications of a Modular Open Magnetosphere Model

GEM：模块化开放磁层模型的应用

• 批准号: 9501898
• 负责人: Thomas Hill
• 金额: $ 22.5万
• 依托单位: William Marsh Rice University
• 依托单位国家: 美国
• 项目类别: Continuing Grant
• 财政年份: 1995
• 资助国家: 美国
• 起止时间: 1995-08-01 至 1998-07-31
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=9501898&HistoricalAwards=false
• 关键词: GEM; Applications; Modular; Open; Magnetosphere

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.

拟议的工作将适用于开放磁层的现有模块化模型，以解决对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以下问题进行预测性理解：（1）太阳风等离子体通过向阳面磁层尖点的注入;（2）外部或内部施加的极帽配置的时间变化;以及（3）由近北向行星际磁场（IMF）驱动的反向对流。 所提出的方法结合了物理-数值模拟与航天器数据分析。 该模型是在过去十年中在GEM计划的部分支持下开发的，描述了从磁层顶到极地电离层沿着相互连接的磁场线的太阳风电场的定量映射。 一个机器便携式，用户友好的版本，这个模型的稳态应用程序最近已提供给创业板研究界。 这个模型最近的扩展允许放宽的稳态假设的时间依赖性的应用。 第一个应用，尖点离子注入的建模，涉及到与T。Onsager将他的Liouville映射程序与模块化开放磁层模型相结合，以产生对尖点离子分布的定量真实模拟，用于在一般范围的输入太阳风/IMF条件下与真实的航天器数据进行比较。 本研究旨在阐明太阳风等离子体注入向阳侧磁层顶形成尖点和邻近边界特征的机制。 第二个应用程序将探讨两种类型的准静态时间演变的极冠，外部驱动的太阳风/IMF的变化和内部驱动的磁尾动力学传达到电离层的电场映射从尾部合并线。 这项研究将利用极地帽的独特性质，不仅作为观测站点，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.合作。 Crooker开发了一个定量模型的overdripped瓣配置提出了她的解释，否则神秘的观测向日对流puperies开放瓣场线连接到太阳风期间的间隔近北IMF。 这一现象以及相关的北向IMF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。