Collaborative Research: Validating Global Magnetospheric Models with Theoretical Magnetograms

这是莱斯大学和密歇根大学之间的一个合作项目，旨在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计算地面磁干扰模式。该模块将利用电离层和内磁层的电流分布，以及理论模型提供的远离地球表面的全球磁场规格，计算整个磁观测站网络中模拟磁场干扰的时间序列（即理论磁图）。该模块的基础是一种方法，该方法结合了有限体积上Biot-Savart定律的数值积分和体积外部未指定电流产生的场的标量势表示。这种方法试图考虑磁层-电离层系统中的所有主要电流，包括地面感应电流、场向电流和部分环电流，以及外磁层和太阳风中的大范围电流。因此，对于给定的模型，计算得到的地面扰动场可能是最真实的。作为一种通用工具，拟议的模块将提供比较各种模型的方法，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。在项目实施阶段，将利用地磁图计算模块探索与地球环电流相关的几个问题。传统上，环电流模型已经通过Dst指数及其与总粒子能量的关系（Dessler-Parker-Sckopke关系）间接地对地面观测进行了测试。新的计算机器将允许考虑磁场时空变化的更详细的模型磁图比较。这些比较将为以下物理问题提供新的信息：(1)磁层-电离层耦合以及在地磁风暴主阶段形成的部分环电流的电离层闭合路径；(2)自洽电导影响闭合路径的机制以及电离层电流的反馈如何导致磁层电流的改变；(3)定量确定构成Dst指数的电流，这将有助于解决有关该指数物理意义的持续争议。这项提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地面磁力计站的数据。提高我们对电离层-磁层系统的认识，将导致创造更可靠的空间天气代码，这将有利于社会。该项目还为研究生和博士后提供教育支持。

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.