GEM: Comprehensive Assessment of the Space Weather Modeling Framework for Magnetic Field Mapping

全球磁流体动力学（MHD）模型是从电离层到磁层特征映射的最自洽的方法。然而，独立的MHD模型不能解释磁层内部的动力学环电流物理，这严重影响了制图的准确性。将内部磁层模型与全球MHD模型耦合是建立可靠的制图手段的重要一步。MHD模型的其他特征，如各向异性压力，可以更好地描述磁重联等磁层动力学的一些特征，也可以改善制图。空间天气模式框架（SWMF）的最新发展包括实现双向耦合内磁层模式和全球MHD模式，块自适应树型太阳风roe型逆风方案（BATSRUS）。BATSRUS模型最近也得到了扩展，纳入了更复杂的物理特性，如各向异性压力、多物质和多流体。本项目将把模拟结果与各种观测结果和代理数据进行比较，如开放和封闭磁场线的边界、等离子体对流方向反转的位置以及高能粒子各向同性和各向异性俯仰角分布的边界。该项目将调查哪种模型最能描述各种地磁条件下的观测结果，并将确定与该模型相关的物理特性是改进的关键。电离层与磁层之间的映射是地球空间系统研究中的一个重要而又困难的问题。与制图相关的不确定性阻碍了我们对导致重要空间天气事件的基本物理机制的理解。该项目的目的是评估现有制图技术的弱点，并确定电离层/磁层系统的全球模拟与实际制图相比如何。

Global magnetohydrodynamic (MHD) models are the most self-consistent way of mapping features from the ionosphere to the magnetosphere. However, stand-alone MHD models cannot account for the kinetic ring current physics in the inner magnetosphere, which strongly affects the accuracy of mapping. Coupling inner magnetosphere models with global MHD models is an important step forward in establishing a reliable means of mapping. Other features of MHD models, such as anisotropic pressure can better describe some features of magnetospheric dynamics such as magnetic reconnection and may improve mapping as well. Recent developments of the Space Weather Modeling Framework (SWMF) include implementation of two-way coupled inner magnetosphere models and the global MHD model, Block Adaptive Tree Solar-wind Roe-type Upwind Scheme (BATSRUS). The BATSRUS model has also recently been extended to incorporate more sophisticated physics, such as anisotropic pressure, multi-species and multi-fluid. This project will compare the simulation results with various observations and proxies, such as the boundary between open and closed magnetic field lines, the location of the reversal in the direction of plasma convection and the boundary between isotropic and anisotropic pitch-angle distributions of energetic particles. The project will investigate which model describes the observations best under various geomagnetic conditions, and will identify what physics associated with that model is the key to the improvement. Mapping between the ionosphere and the magnetosphere is an important but difficult problem in studying the geospace system. Uncertainty associated with mapping prevents our understanding of fundamental physical mechanisms that are responsible for important space weather events. The objective of this project is to assess the weaknesses of existing mapping techniques and determine how global simulations of the ionosphere/magnetosphere system compare with reality in terms of mapping.