伴随地球磁尾磁场重联的电子加速研究

Magnetic reconnection is paid close attention because it is one important energy dissipation in the space plasma of solar-terrestrial environment. Magnetic reconnection can transfer magnetic energy into plasma thermal and kinetic energy in short time period, therefore it would accelerate and heat the particles. Energetic electrons are important offspring during magnetic reconnection. Many problems how the electros be accelerated need to resolve until now. This program will focus on the electron acceleration mechanism and process during magnetic reconnection. Using the Cluster and THEMIS observations, we will investigate electron acceleration during magnetic reconnection, including: reveal the acceleration effectiveness in the different regions (such as primary island, secondary island, magnetic flux pileup region separatrx, and thin current sheet etc.); explore which physical parameters would affect the electron acceleration (reconnection electric field, normal electric field, plasma velocity, the amplitude of wave/turbulence, thickness of current sheet, parallel current density and the location when magnetic reconnection occurs etc.) and what favorable physical condition to efficiently accelerate the electrons; analyze the process of electron acceleration during the different types of magnetic reconnection. These results are helpful to explore the energy release mechanism during magnetic reconnection and the origin of energetic electron in the magnetotail.

磁场重联作为日地空间等离子体中一种非常重要的能量快速释放方式而倍受关注，它能够在短时间内把磁场的能量快速地转换为等离子体的动能和热能，从而加速和加热粒子。伴随磁场重联经常有高能电子产生，它是重联的重要产物，但在重联过程中如何加速电子是当今空间物理一直悬而未决的难点及热点问题。本项目以伴随地球磁尾磁场重联的电子加速过程和机制为主要研究内容。通过Cluster和THEMIS等卫星的观测数据，揭示电子在不同区域（即主要磁岛、次级磁岛、通量堆积区、分形线和薄电流片等）的加速效率；探索影响电子加速的物理参数，即重联电场，法向电场，等离子体流速，波动与湍流的强度，电流片的厚度，平行电流密度和重联发生位置等，探寻适宜加速电子的物理环境；分析在不同类型磁场重联中电子加速的过程。研究结果有助于揭示重联过程中能量的释放机制和地球磁尾高能电子的起源。

项目自2015年1月开始执行以来，按照研究计划执行，项目进展顺利，完成了申请书计划的研究内容。基于Cluster和MMS卫星观测数据及数值模拟技术，在磁场重联动力学过程、波动特性、结构等方面，主要揭示了重联jet中次级重联的详细过程；首次发现了重联分形线附近局地形成的磁通量管，在湍动磁鞘等离子体观测到离子尺度的磁岛；首次发现重联区域两种不同类型的哨声波，并得到重联区域哨声波的统计分布特性；与重联相关的偶极化锋面处观测到大振幅电磁波，并详细分析其玻粒相互作用过程，探究了偶极化锋面处能量转换过程，发现由磁场能量向粒子转换。这些研究成果对于帮我我们理解磁场重联区域电子动力学过程和磁层动力学过程，以及空间天气建模等具有重要的科学意义。