Collaborative Research: GEM--Thermal Electron Anisotropy in the Earth's Magnetotail

空间等离子体物理学最重要的问题之一是理解高能带电粒子是如何产生的。在被称为电流片的地磁场区域中，人们提出了各种各样的机制来加速电子。这个项目将有助于区分这些理论，以帮助确定哪些理论在磁层中起作用。这与《国家空间天气计划》直接相关，因为这项工作可以建立更好的空间天气模型和预报，从而影响国家商业和国防卫星以及天基通信。此外，研究生和本科生将参与研究。本项目量化了电子热各向异性对磁尾电流片结构的影响，研究了电子热各向异性特征随地磁活动的变化。各向异性电子居群可产生强电流（由粒子曲率漂移引起），并可作为各种电磁波发射的能量源。该项目使用了五个航天器任务（Geotail, Cluster， THEMIS， ARTEMIS和MMS）的观测数据，覆盖了整个磁尾在10到80个地球半径的径向距离内。利用多年来在近地和中磁尾的THEMIS/ARTEMIS观测资料，研究了不同磁尾结构下电子热各向异性的径向分布以及电子各向异性电流对电流片结构的影响。此外，利用高分辨率等离子体测量的MMS观测将首次从统计学上揭示电子各向异性居群的精细结构及其对电流密度的贡献。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。

One of the most important problems of space plasma physics is understanding how high-energy charged particles are generated. There are a huge variety of mechanisms suggested for accelerating electrons in the region of the geomagnetic field known as the current sheet. This project will help distinguish between these theories to help determine which are at work in the magnetosphere. This is directly relevant to the National Space Weather Plan, since the work can lead to better models and forecasts of space weather, which affects national commercial and defense satellites and space-based communications. Additionally, graduate and undergraduate students will participate in the research.This project quantifies the impact of the electron thermal anisotropy on the magnetotail current sheet structure and investigates the variation of characteristics of electron thermal anisotropy with geomagnetic activity. The anisotropic electron population can be responsible for generation of strong currents (induced by particle curvature drifts) and can serve as an energy source for various electromagnetic wave emissions. The project uses observations from five spacecraft missions (Geotail, Cluster, THEMIS, ARTEMIS, and MMS) covering the entire magnetotail within the radial distances from 10 to 80 Earth radii downtail. Using several years of THEMIS/ARTEMIS observations in the near-Earth and middle magnetotail, the work studies both the radial distribution of the electron thermal anisotropy and the impact of electron anisotropic currents on current sheet structure for different magnetotail configurations. Moreover, using MMS observations with the high-resolution plasma measurements the work will for the first time statistically reveal the fine structure of the electron anisotropic population and its contribution to the current density.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.