Local physics control of the x-line orientation in three-dimensional asymmetric magnetic reconnection

磁重联是空间等离子体中最重要的能量转换和传输过程之一。这个项目旨在回答一个与我们对磁重联的理解有关的基本问题：是否有一个简单的原理来确定非对称电流片中重联x线的方向？根据我们目前对磁重联的理解，这个基本问题的解决方案仍然不清楚，该项目的目标是使用Blue Waters来解决这个问题。最终，该项目的目标是了解不对称磁重联本身的三维(3D)性质，这是寻求预测地球磁层顶磁重联的位置和方向的重要一步。此外，增加对x线的了解将使空间科学家能够更准确地估计从太阳风到地球磁层的通量转移的效率。此外，本文提出的工作对于NASA磁层多尺度任务(MMS)第一阶段的白天重联研究也是适时的。该项目的目标是围绕3Dx线在非对称重联中的局域物理控制，这对地球磁层顶有直接应用。该项目将解决以下问题：a)控制3Dx线方向的基本物理是什么？B)3DX线是如何展开的？它有内在的范围吗？C)反磁漂移如何影响3Dx线的取向和运动？D)斜撕裂不稳定性和由此产生的通量绳起了什么作用？重新连接x线的发展需要一个完全的动力学描述，因此本项目将使用粒子在单元(PIC)程序，VPIC，它是在Blue Waters超级计算机上优化的。对于3D模拟，该项目的创新方法是使用局部扰动来诱导单个x线，以便x线有足够的自由选择其方向。

Magnetic reconnection is arguably one of the most important energy conversion and transport processes in space plasmas. This project aims to answer a fundamental question related to our understanding of magnetic reconnection: is there a simple principle that determines the orientation of the reconnection x-line in a asymmetric current sheet? The solution of this basic question remains unclear with our current understanding of magnetic reconnection, and the project aims to use Blue Waters to resolve this issue. Ultimately, the project's goal is to develop an understanding on the three-dimensional (3D) nature of asymmetric magnetic reconnection itself, which is an important step in the quest for predicting the location and orientation of magnetic reconnection at Earth's magnetopause. Moreover, increased understanding of x-line will enable space scientists to more accurately estimate the efficiency of flux transfer from solar wind to Earth's magnetosphere. In addition, the work proposed here is timely to the study of dayside reconnection during the 1st phase of NASA's Magnetospheric Multiscale Mission (MMS). The goal of the project centers around the local physics control of 3D x-line in asymmetric reconnection, which has a direct application to terrestrial magnetopause. The project will address the following questions: a) What is the underlying physics that control the 3D x-line orientation? b) How does the 3D x-line spread? Does it have an intrinsic extent? c) How does the diamagnetic drift affect the orientation and the motion of a 3D x-line? d) What role do oblique tearing instabilities and the resulting flux ropes play?The development of reconnection x-line requires a fully kinetic description, hence this project will employ the particle-in-cell (PIC) code, VPIC, which is optimized on the Blue Waters supercomputer. For 3D simulations, the project's innovative approach is to induce a single x-line using a localized perturbation, so that the x-line has sufficient freedom to choose its orientation.