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

GEM：GEM 项目的基于数据的地球空间磁场模型

• 批准号: 9501463
• 负责人: Nikolai Tsyganenko
• 金额: $ 17.14万
• 依托单位: Raytheon Technical Services Company
• 依托单位国家: 美国
• 项目类别: Continuing Grant
• 财政年份: 1996
• 资助国家: 美国
• 起止时间: 1996-02-01 至 1999-01-31
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=9501463&HistoricalAwards=false
• 关键词: GEM; Data; Based; Models; Geospace

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.

建议开发一种新的基于数据的地球磁层磁场模型。地球空间等离子体环境建模是GEM项目的本质，其特殊任务之一是准确地表示远处的地磁构形。该模式将专门为满足地球空间环流模式的需要而设计，为社区提供灵活的工具来处理磁层电流系统，并定量地表示它们对总场的贡献。拟议的研究将基于几十年来积累的许多航天器的磁力仪数据，并将使用复杂的数学方法，允许灵活地表示观测到的场。作为位置、地球偶极子倾角、太阳风特征、极冠面积和适当的地磁扰动指数的连续解析函数，新模型将对大范围内的地磁场提供真实的定量描述。该项目的主要目标之一将不仅是表示平均磁层配置，而且还表示其大范围的时间变化。具体地说，它旨在对以下现象进行定量模拟：(1)磁层顶对太阳风的响应压缩/扩展，(2)由行星际磁场引起的亚暴增长阶段磁通量的逐渐重新分布，以及(3)导致先前拉伸的构型崩溃的亚暴电流系统的形成。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。