GEM: Multi-scale Empirical Geomagnetic Field Modeling

几十年来，从空间仪器收集的数据已经建立了复杂的地球磁场经验模型。这些模型是对基于物理学的第一性原理模型的必要补充。该项目的目标是改进一个这样的磁层经验模型，以包括较长的太阳周期时间尺度和较短的亚暴时间尺度。这将极大地增进对近地环境的了解，这对于最终保护现代技术至关重要。该项目旨在从根本上升级风暴尺度经验地磁场TS 07D模型，使其包括比风暴更长和更短时间尺度上的地磁变化。前者是由太阳辐射（用F10.7通量量化）的太阳周期变化引起的。后者代表了极光指数量化的亚暴效应。这项工作将解决什么样的影响的太阳辐照度的地磁场和底层电流系统的结构，以及如何亚暴变薄和磁尾的双极化影响的经验图片的地磁场。新的模型升级，这是为了回答这些问题，采用不同的电流片厚度值的赤道电流的多重扩展，以及改进的描述的字段对齐的电流系统。它结合了系统科学的方法，当一些全球参数的磁层的经验重建的演变，与基于物理学的方法，这是用来约束时空尺度和结构的经验模型。

Sophisticated empirical models of the Earth's magnetic field have been built over decades of data collected from spaceborne instruments. These models are a necessary compliment to the physics-based first-principles models. The project goals are to improve one such empirical model of the magnetosphere to include longer, solar cycle time scales and shorter, substorm time scales. This will vastly improve understanding of the near-Earth environment, which is important for ultimately protecting modern technology. The effort will promote hands-on research training for a graduate student and a summer student.This project is to fundamentally upgrade the storm-scale empirical geomagnetic field TS07D model to include geomagnetic variations on time scales both longer and shorter than those of storms. The former are caused by the solar cycle variations of the solar radiation (quantified by the F10.7 flux). The latter represent substorm effects quantified by auroral indices. The work will address what the impact of the solar irradiance on the structure of the geomagnetic field and underlying current system is, and how substorm thinning and dipolarization of the magnetotail affect the empirical picture of the geomagnetic field. The new model upgrade, which is aimed to answer these questions, employs multiple expansions of equatorial currents with different current sheet thickness values as well as an improved description of the field aligned current system. It combines the system science approach, when the evolution of a few global parameters of the magnetosphere is reconstructed empirically, with the physics-based approach, which is used to constrain spatio-temporal scales and structure of the empirical model.