Electrons in the Geomagnetic Tail

地磁尾中的电子

• 批准号: 9312467
• 负责人: Maha Ashour-Abdalla
• 金额: $ 5万
• 依托单位: University of California-Los Angeles
• 依托单位国家: 美国
• 项目类别: Standard Grant
• 财政年份: 1994
• 资助国家: 美国
• 起止时间: 1994-02-01 至 1996-01-31
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=9312467&HistoricalAwards=false
• 关键词: Electrons; Geomagnetic; Tail

9312467 Ashour-Abdalla The proposed theoretical investigation is to calculate electron distributions in the geomagnetic tail to the Earth's magnetosphere and to evaluate the local and global problem of charge neutrality between electrons and ions. Although the dynamics of ions in the magnetotail has been the subject of extensive theoretical investigations using single particle orbit calculations, hybrid simulations, and magnetohydrodynamic fluid simulations, electron dynamics have been virtually ignored. Yet, the most fundamental aspect of a plasma - the establishment and maintenance of charge neutrality - depends on electron behavior. Some electrons move at high speeds and rapidly traverse large volumes of space; the establishment of local charge neutrality depends on both the global sources and sinks of electrons and the large scale structure of the electric and magnetic fields in the tail. Until now, no scientific methodology has existed capable of addressing global transport and calculating the local distributions of electrons in the tail. In the proposed large scale kinetics approach, starting from various source regions, electrons will be allowed to propagate throughout the entire volume of the magnetotail along trajectories which are determined using model electromagnetic fields to represent the tail configuration. The local electron distribution function will be calculated by summing the contributions of each trajectory passing through the local spatial region, and the electron density will be compared to the local ion density (which is similarly calculated by the large scale kinetics technique) to determine the extent of charge neutrality violation. Parallel electric fields will be added to the electromagnetic field model, and will be adjusted to obtain the closet reasonable balance between electron and ion charge densities. The potential significance of this proposed is profound in that, with its success we could for the first time directly asses s the problem of charge neutrality in a space plasma, determine the large scale potential electric fields required to maintain charge neutrality, and establish the extent to which charge neutrality demands the exchange of electrons between the tail plasma and the ionosphere. ***

9312467阿苏尔-阿卜杜拉拟议的理论研究是计算地球磁层的地磁尾部中的电子分布，并评估电子和离子之间电荷中性的局部和全球问题。虽然磁尾离子的动力学一直是广泛的理论研究的主题，使用单粒子轨道计算、混合模拟和磁流体动力学模拟，但电子动力学实际上被忽略了。然而，等离子体最基本的方面--电荷中性的建立和维持--取决于电子的行为。一些电子以高速移动并迅速穿越大量空间；局部电荷中性的建立既取决于全球电子的源和汇，也取决于尾部电场和磁场的大尺度结构。到目前为止，还没有一种科学方法能够解决全球交通问题并计算尾部电子的局部分布。在所提出的大尺度动力学方法中，从各个源区开始，电子将被允许沿着使用模型电磁场来表示尾部构型的轨迹在整个磁尾体积中传播。局部电子分布函数将通过对通过局部空间区域的每个轨迹的贡献相加来计算，电子密度将与局部离子密度(类似地由大尺度动力学技术计算)相比较，以确定电荷中性破坏的程度。将平行电场添加到电磁场模型中，并对其进行调整，以获得电子和离子电荷密度之间的合理平衡。这一提议的潜在意义是深远的，因为它的成功，我们可以第一次直接评估S在空间等离子体中的电荷中性问题，确定保持电荷中性所需的大尺度势电场，并确定电荷中性需要在尾部等离子体和电离层之间交换电子的程度。***