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映射特征的最自洽方式。 然而，独立的MHD模型不能解释内磁层中的动力学环电流物理，这严重影响了映射的准确性。将内磁层模型与全球MHD模型相结合是建立可靠的测绘手段的重要一步。MHD模型的其他特征，如各向异性压力，可以更好地描述磁层动力学的一些特征，如磁重联，并可能改善映射。空间气象建模框架（SWMF）的最新发展包括实施双向耦合内磁层模型和全球磁流体模型、块自适应树太阳风Roe-type逆风方案（BATSRUS）。BATSRUS模型最近也得到了扩展，以纳入更复杂的物理学，如各向异性压力，多物种和多流体。该项目将把模拟结果与各种观测和代用指标进行比较，如开放和封闭磁场线之间的边界、等离子体对流方向的反转位置以及高能粒子的各向同性和各向异性俯仰角分布之间的边界。该项目将调查在各种地磁条件下哪种模型最好地描述了观测结果，并将确定与该模型相关的物理学是改进的关键。电离层与磁层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。与测绘相关的不确定性妨碍了我们对造成重要空间气象事件的基本物理机制的理解。该项目的目标是评估现有测绘技术的弱点，并确定电离层/磁层系统的全球模拟在测绘方面如何与现实相比较。

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.