磁尾三维磁重联过程中的等离子体波动研究

Magnetic reconnection is very important to many key processes of space physics,such as solar flare/CME, solar wind - magnetophere interaction, substorm, etc. Based on prevous works on 3D reconnection by a small research group in Peking University,We will continue the research on 3D reconnection events in geomagnetotail. Using the data in situ mearsured by Cluster spacecraft the the coming MMS project, We will focus on data analysis of the palsma waves in 3D reconnection region, which specially locate near the separatrix and separator (null-null line), such as the polarization properties, the wave verctors and the dispersion relation, the mechanism of excitation and dissipation of those wave modes, the possible processes of wave mode convection, etc. The case study and statistical research will be co-applied. Furthermore, we will try to get the theoretical analysis, and also the estimation resultes by in situ measurement data, of the anomalous resistivities due to wave-particle interactions, specilly rlated to the Lower-hybrid waves, Whislter modes, as well as the kinetic Alfven waves in different regions, different processes of 3D reconnection cases. These results will help to find the trigger mechanism, the key issues to determine the magnitude of reconnection rate, as well as the dynamics of 3D reconnection in magnetotail.

磁尾磁重联在亚暴等诸多磁层物理过程中起着重要作用。作为一个良好的无碰撞磁重联实验室，磁尾电流片是局地三维磁重联观测研究的重点区域之一。本项目作为"日地空间磁场重联亮点研究方向"的项目群成员，拟在北大三维重联研究团队（濮祖荫、王晓钢和肖池阶）的前期工作基础上，利用Cluster卫星和即将升空的MMS计划的多颗卫星观测数据，以三维磁重联过程中的等离子体波模为中心，从磁场拓扑结构、等离子体波模性质、以及波-粒相互作用引起的反常电阻等方面，对三维磁重联开展观测和理论研究。重点将基于观测数据的磁场重构结果，研究零点连线上磁场强度大小分布，在三维重联的框架下研究"反平行重联"与"分量重联"的关系；对三维磁重联分形面和分形线区域等离子体波模的频率、波矢量、偏振及色散关系等进行观测分析；同时对低混杂波、哨声波和动理学Alfven波的反常电阻进行理论与观测研究；为建立三维磁重联的物理模型进一步提供观依据。

本项目结合Cluster和MMS卫星观测，在磁尾磁重联事件分析中，发现两个相继观测到的分量重联和反平行重联事件很可能是同一个三维磁重联事件，分别对应在三维零点连线和零点附近的部分现象；发现剪切流对重联有重要影响；观测到重联扩散区内部存在哨声波，以及高于低混杂频率的右旋电磁波模。此外，我们还通过高精度自适应二维粒子模拟程序，发现分形线附近有重联告诉电子流激发的准单色电磁模式，以及由Hall效应引起的哨声波。这些观测和模拟结果，有望加深理解磁重联的基本物理过程，特别是三维磁重联的几何拓扑结构和动力学过程的理解。