GEM: Dipolarization Fronts and Reconnection Onset in Realistic Models of the Magnetotail

磁层是非常动态的。磁层亚暴每隔几小时发生一次。从地球上看，它们就像极光展示一样可见。在空间中，与磁层亚暴有关的主要现象之一是产生偶极锋面。这些都是从磁尾向地球传播的垂直于等离子体片的磁场分量的快速增加。它们被称为偶极阵面(DFS)，因为磁场呈现出一种更类似于偶极的构型。对DFS最常见的解释是，它们与磁重联有关。这项工作与其他有关电流片的研究有关，如行星磁层、太阳日冕和太阳风中的电流片。这项建议的目标是在现实的尾部模型中研究DFS的形成。该团队建议构建新的自洽2D电流片平衡，类似于在亚风暴增长阶段观察到的平衡。他们将使用动力学理论和具有真实电子与离子质量比的二维粒子在胞(PIC)模拟来研究它们对重联的稳定性。这将扩展到3D PIC模拟，以研究尾部等离子体响应的整个光谱，包括撕裂、气球/互换和拍打运动。将把动力学图像与全球磁流体力学模型的结果进行比较，目的是将动力学物理纳入全球模型。应用物理实验室为暑期学生提供了一个项目来帮助他们进行研究。

The magnetosphere is very dynamic. Magnetospheric substorms occur every few hours. Viewed from the Earth they are visible as auroral displays. In space one of the main phenomena associated with magnetospheric substorms is the generation of dipolarization fronts. These are rapid increases in the component of the magnetic field normal to the plasma sheet that propagate from the magnetotail toward the Earth. They are called dipolarization fronts (DFs) since the magnetic field assumes a more "dipole like" configuration. The most common explanation for DFs is that they are related to magnetic reconnection. This work is relevant to other studies of current sheets such as those in planetary magnetospheres, the solor corona and the solar wind. The goal of this proposal is to investigate the formation of DFs in realistic tail models. The team proposes to construct new classes of self-consistent 2D current sheet equilibria similar to those observed during the growth phase of substorms. They will investigate their stability to reconnection by using kinetic theory and 2D particle in cell (PIC) simulations with realistic electron to ion mass ratio. This will be extended to 3D PIC simulations to investigate the whole spectrum of tail plasma responses including tearing, ballooning/interchange and flapping motions. The kinetic picture will be compared with that from global magnetohydrodynamic models with the goal of including the kinetic physics in the global models. The Applied Physics Laboratory has a program for summer students to help with the research.