Collaborative Research: Validating Global Magnetospheric Models with Theoretical Magnetograms

这是莱斯大学和密歇根大学的一个合作项目，目的是开发和实施一个灵活的计算模块，该模块将根据各种理论空间物理模型的输入来计算地面磁骚扰模式。该模块将使用电离层和内磁层中的电流分布以及理论模型提供的远离地球表面的全球磁场规格，计算整个磁性观测站网络上模拟磁场扰动的时间序列(即理论磁力图)。该模块的基础是将有限体积上毕奥-萨伐尔定律的数值积分与体积外不明电流产生的场的标量势表示相结合的方法。这一方法试图考虑磁层-电离层系统中的所有主要电流，包括接地感应电流、场向和部分环电流以及外磁层和太阳风中的大尺度电流。因此，对于给定的模型，计算的地面扰动场将是最真实的。作为一种通用工具，拟议的模块将提供比较各种模型的手段，包括环流模型和对流模型，以及目前正在开发的综合全球磁层-电离层-热层模型。在该项目的实施阶段，将利用地磁图计算模块探讨与地球环电流有关的几个问题。传统上，环电流模型通过DST指数及其与总粒子能量的关系，通过Dessler-Parker-Sockopke关系，间接地与地面观测进行测试。新的计算机制将允许更详细的模型磁图比较，它同时考虑了磁场扰动场的时间和空间变化。这些比较将提供有关下列物理问题的新信息：(1)磁层-电离层耦合和在地磁暴主相产生的部分环电流的电离层关闭路径；(2)自洽电导影响这一关闭路径的机制，以及来自电离层电流的反馈如何导致磁层电流的改变；(3)对参与DST指数的电流的定量确定，这将有助于解决目前关于该指数物理意义的争议。这项拟议的研究有几个更广泛的影响。最重要的是，它允许更有效地利用来自大量陆基磁力计测站的数据。增进我们对电离层-磁层系统的了解将产生更可靠的空间气象代码，这将造福社会。该项目还为研究生和博士后研究员提供教育支持。

This is a collaborative project between Rice University and the University of Michigan to develop and implement a flexible computational module that will calculate ground magnetic disturbance patterns, based upon input from various theoretical space physics models. The module will compute time-series of simulated magnetic field disturbances across the network of magnetic observatories (i.e., theoretical magneto grams) using a distribution of currents in the ionosphere and inner magnetosphere, and a specification of the global magnetic field far from the Earth's surface, provided by a theoretical model. The basis for the module is a method that combines numerical integration of the Biot-Savart law over a finite volume with a scalar potential representation of the field produced by unspecified currents external to the volume. This approach attempts to take into account all major currents in the magnetosphere-ionosphere system, including ground induction currents, field-aligned and partial ring currents, and large-scale currents in the outer magnetosphere and solar wind. Thus the computed ground disturbance fields will be the most realistic possible for a given model. Intended as a general-use tool, the proposed module will provide the means of comparing a broad range of models, including ring current models and convection models, as well as comprehensive global magnetosphere-ionosphere-thermosphere models currently under development. In the implementation phase of the project, several issues related to the Earth's ring current will be explored with the ground-magnetogram computational module. Traditionally, ring current models have been tested against ground-based observations indirectly, through the Dst index and its relationship to the total particle energy via the Dessler-Parker-Sckopke relation. The new computational machinery will allow much more detailed model-magnetogram comparisons that consider both the temporal and spatial variation of the magnetic disturbance field. The comparisons will provide new information on physical issues such as: (1) Magnetosphere-ionosphere coupling and the ionospheric closure path for the partial ring current that develops in the main phase of a geomagnetic storm; (2) The mechanism by which a self-consistent conductance influences this closure path and how the feedback from the ionospheric current results in a modification of the magnetospheric currents; (3) Quantitative identification of the currents that contribute to the Dst index, that will help resolve the ongoing controversy about the physical meaning of that index. There are several broader impacts of this proposed research. Foremost is that it allows a more effective utilization of the data from the vast array of ground based magnetometer stations. Advancing our knowledge of the ionosphere-magnetosphere system will result in the creation of more reliable space weather codes, which will benefit society. The project also provides educational support for graduate students and a postdoctoral fellow.