GEM: Data-Based Models of the Geospace Magnetic Field for the GEM Project

建议开发一个新的地球磁层磁场数据模型。 地球空间等离子体环境建模是GEM项目的核心，其特殊任务之一是精确表示远距离地磁场结构。 该模型将专门设计，以满足地球空间环流模型的需要，为业界提供灵活的工具，以处理磁层电流系统，并从数量上表示它们对总磁场的贡献。 拟议的研究将以许多航天器几十年来积累的磁力计数据为基础，并将使用复杂的数学方法，以便灵活地表示观测到的磁场。 新的模型将提供一个现实的量化描述的地磁场的范围很广的距离，作为一个连续的分析功能的位置，地球的偶极子倾角，太阳风的特点，极冠面积，和适当的地磁扰动指数。 这个项目的主要目标之一将是不仅代表平均磁层配置，而且代表其大尺度的时间变化。 具体地说，它旨在定量地模拟这样的现象， （一） 磁层顶的压缩/膨胀 太阳风阵风， (ii)磁通量的逐渐重新分布 亚暴增长阶段，由行星际 磁场和 (iii)亚暴电流系统的形成 导致了之前被拉伸的 配置. 这项工作的主要成果将是用于推导时变模型磁场的计算机代码。

It is proposed to develop a new data-based model of the Earth's magnetospheric magnetic field. Modeling the geospace plasma environment is the essence of the GEM project, and one of its special tasks is an accurate representation of the distant geomagnetic configuration. The model will be specifically designed to meet the needs of the Geospace Circulation Model providing the community with flexible tools to handle magnetospheric current systems and quantitatively represent their contributions to the total field. The proposed study will be based on magnetometer data from many spacecraft, accumulated over tens of years, and will use sophisticated mathematical methods, allowing a flexible representation of the observed fields. The new model will provide a realistic quantitative description of the geomagnetic field for a wide range of distances, as a continuous analytical function of the position, Earth's dipole tilt angle, solar wind characteristics, the polar cap area, and appropriate geomagnetic disturbance indices. One of the principal goalq of this project will be to represent not just the average magnetospheric configurations, but also its large- scale time variations. Specifically, it is intended to quantitatively model such phenomena as (i) compression/expansion of the magnetopause in response to solar wind gusts, (ii) gradual re-distribution of the magnetic flux during the substorm growth phase, induced by the interplanetary magnetic field, and (iii) formation of the substorm electric current system leading to the collapse of the previously stretched configuration. The main product of this effort will be computer codes for deriving the time-varying model magnetic field.