The Nonorthogonal X-line in a Small Guide-field Reconnection Event in the Magnetotail
The Nonorthogonal X-line in a Small Guide-field Reconnection Event in the Magnetotail
复制标题
DOI：
10.3847/1538-4357/acd4ba
复制
发表时间：
2023-06
期刊：
影响因子：
--
通讯作者：
Y. Qi;R. Ergun;N. Pathak;Tak Chu Li;S. Eriksson;A. Chasapis;S. Schwartz;N. Ahmadi;T. Vo;D. Newman;M. Usanova;F. Wilder;J. Shuster
中科院分区：
文献类型：
--
作者：
Y. Qi;R. Ergun;N. Pathak;Tak Chu Li;S. Eriksson;A. Chasapis;S. Schwartz;N. Ahmadi;T. Vo;D. Newman;M. Usanova;F. Wilder;J. Shuster
磁场重联是一个基本的等离子体过程，几十年来，人们一直用解析理论、数值模拟、原位观测和实验室实验对它进行研究。已经建立的描述磁场重联的模型通常假设重联平面垂直于电流片，在该平面中反平行磁场湮灭。湮灭点，也称为X点，形成一条x线，它被认为垂直于重联平面。最近，一项利用磁层多尺度使命观测的新研究通过提供x线不一定与重联平面正交的证据，挑战了我们对磁重联的理解。在这项研究中，我们报告了第二个非正交的X线事件与以前的案例研究中，类似的功能，支持剪切的X线现象是不是一个异常事件。我们采用了详细的方向导数分析，以确定x线方向，并表明，即使与非正交的x线的面内重联特性保持良好。此外，我们发现x线倾向于跟随电流片一侧的磁场，这表明电流片上的不对称性。我们讨论的可能性，非正交的x线产生的重联的两个方面之间的相互作用：宏观磁场拓扑结构和微观粒子动力学。
Magnetic reconnection is a fundamental plasma process that has been studied with analytical theory, numerical simulations, in situ observations, and laboratory experiments for decades. The models that have been established to describe magnetic reconnection often assume a reconnection plane normal to the current sheet in which an antiparallel magnetic field annihilates. The annihilation points, also known as the X-points, form an x-line, which is believed to be perpendicular to the reconnection plane. Recently, a new study using Magnetospheric Multiscale mission observations has challenged our understanding of magnetic reconnection by providing evidence that the x-line is not necessarily orthogonal to the reconnection plane. In this study we report a second nonorthogonal x-line event with similar features as that in the previous case study, supporting that the sheared x-line phenomenon is not an aberrant event. We employ a detailed directional derivative analysis to identify the x-line direction and show that the in-plane reconnection characteristics are well maintained even with a nonorthogonal x-line. In addition, we find the x-line tends to follow the magnetic field on one side of the current sheet, which suggests an asymmetry across the current sheet. We discuss the possibility that the nonorthogonal x-line arises from an interplay between the two aspects of reconnection: the macroscopic magnetic field topology and microscopic particle kinetics.