GEM: Particle Acceleration by Foreshock Transients

在整个宇宙中，冲击波将粒子加速到相对论速度——在天体物理过程中，在地球附近的空间区域更局部。冲击如何将粒子加速到比它们自身的冲击势能储备更高的能量，这是一个谜。该项目将调查冲击进入磁层之前等离子体流动的不规则性，研究等离子体气泡和热流异常。该项目的成果可直接应用于空间天气模型；因此，它解决了国家空间天气行动计划中规定的目标之一。该项目还将有助于了解整个宇宙的冲击加速度。三名早期职业研究人员和一名研究生将获得资助。主要目标是(i)确定上游电子能量对高能粒子向内穿透造成的空间天气现象的作用；（ii）为费米型激波加速过程的经典预加速需求提供新的见解。首次获得了来自前震区的高质量和高分辨率的THEMIS和MMS数据。THEMIS提供了大尺度磁性结构以及高频磁波动和超热粒子（25 keV）的数据，而MMS能够分辨小尺度（10-100 km）高时间分辨率（30 -150 ms），提供微观尺度和电子动力学量。这些观测将由Cluster和DMSP补充，它们监测尖端的高能粒子通量，并从所有天空成像仪和nsf资助的superdam数据中提供加速粒子的特征。将这些观察结果结合起来是一项具有挑战性的任务。该方案利用一个经过良好测试的三维全局混合仿真代码来组织数据并达到预期的结果。该奖项反映了美国国家科学基金会的法定使命，并通过使用基金会的知识价值和更广泛的影响审查标准进行评估，被认为值得支持。

Shocks accelerate particles to relativistic speeds throughout the universe – in astrophysical processes and more locally in the region of space near the Earth. It is a mystery how shocks can accelerate particles to energies higher than their own shock potential energy reserve. This project will investigate irregularities in plasma flows ahead of shocks moving into the magnetosphere, studying plasma bubbles and hot flow anomalies. The results of this project have direct applications in space weather models; it thus addresses one of the goals set out in the National Space Weather Action Plan. The project will also help understand shock acceleration throughout the universe. Three early career researchers and a graduate student will receive support.The key objectives are (i) to determine the role of upstream electron energization on space weather phenomena that result from inward penetration of energetic particles; and (ii) to provide new insights in the classic pre-acceleration need for Fermi type shock acceleration processes. For the first time high quality and resolution THEMIS and MMS data from the foreshock region are available. THEMIS provides data on large scale magnetic structures along with high-frequency magnetic fluctuations and superthermal particles ( 25 keV), while MMS is capable of resolving small scale (10-100 km) high time resolution (30 -150 ms) providing microscale and electron dynamics quantities. The observations will be supplemented by Cluster and DMSP which monitor the energetic particle flux in the cusp and from all sky imagers and NSF-funded SuperDARN data providing signatures of accelerating particles. Combining these observations is a challenging task. The proposal utilizes a well-tested 3D global hybrid simulation code to organize the data and achieve the desired results.This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.