GEM: Dipolarization and Particle Acceleration at Substorm Onset

GEM：亚暴爆发时的偶极和粒子加速

• 批准号: 1203711
• 负责人: Joachim Birn
• 金额: $ 32万
• 依托单位: SPACE SCIENCE INSTITUTE
• 依托单位国家: 美国
• 项目类别: Continuing Grant
• 财政年份: 2012
• 资助国家: 美国
• 起止时间: 2012-10-01 至 2016-09-30
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=1203711&HistoricalAwards=false
• 关键词: GEM; Dipolarization; Particle; Acceleration; Substorm

This project will use a combination of 3-dimensional magnetohydrodynamic (MHD) and test particle (ions and electrons) simulations to investigate the energization of particles during the unset of a magnetic substorm. Substorm onset in the magnetotail is characterized by a sudden "dipolarization," that is, return from a stretched tail-like to a more dipolar magnetic field, also interpreted as "current disruption." This reconfiguration is associated with a strong induced electric field, which is strongly localized in space as well as in time. The project will examine the relationship between various onset signatures, such as magnetic reconnection, dipolarization, and particle acceleration, and the spatial and temporal properties of energetic particle fluxes. The MHD/test particle simulations will be supplemented by kinetic particle-in-cell (PIC) simulations as well as data analyses. The data that will be used for comparisons with the simulation results will come from the Los Alamos geosynchronous satellites and from the NASA THEMIS mission.Magnetic substorm activity is a special manifestation of a universal plasma and field process, which involves energy storage in magnetic fields and the sudden release of this energy and its conversion to particle energy via magnetic reconnection and its consequences. Understanding the mechanisms by which particles are accelerated to high energies is an essential element of understanding and predicting space weather, as well as for understanding solar and astrophysical eruptive plasma/magnetic field processes.

本计画将结合三维磁流体动力学（MHD）与测试粒子（离子与电子）模拟来研究磁次暴未发生时粒子的运动。磁尾的亚暴开始以突然的“双极化”为特征，也就是说，从一个拉伸的尾巴状磁场返回到一个更偶极的磁场，也被解释为“电流中断”。“这种重新配置与强烈的感应电场有关，该电场在空间和时间上都很强。 该项目将研究各种起始特征之间的关系，如磁重联，偶极化和粒子加速，以及高能粒子通量的空间和时间特性。MHD/试验粒子模拟将通过动力学粒子模拟（PIC）和数据分析进行补充。 将用于与模拟结果进行比较的数据将来自洛斯阿拉莫斯地球同步卫星和美国航天局THEMIS使命。磁亚暴活动是一种普遍等离子体和场过程的特殊表现，它涉及能量在磁场中的储存和这种能量的突然释放以及通过磁重联将其转化为粒子能量及其后果。了解粒子加速到高能的机制是了解和预测空间气象以及了解太阳和天体物理学喷发等离子体/磁场过程的一个基本要素。