伴随偶极化锋面的高能电子加速机制研究

It is helpful to study the energetic electron acceleration in the Earth's magnetotail for understanding the energy release and transportation process in the magnetosphere, as well as the source of energetic electrons in the inner magnetosphere, especially the radiation belt. It is also crucial for space weather forecast and research. Magnetotail reconnection is believed as the main source of energetic electrons in the magnetotail, however, it is doubtful whether the narrow diffusion region could account for the energization of large number of electrons. Recent studies demonstrated that electron acceleration associated with magnetic reconnection might occurrs within downstream fast plasma flow far away from the diffuison region. Energetic electron fluxes increases are frequently observed at the dipolarization fronts associated with fast flow. In this program we plan to combine the Cluster and THEMIS multiple satellite observation, and full particle simulation, large scale test particle simulation to reveal the energy release and transportation mechanisms associated with dipolarization front in the fast flow, including multi-scale physics, from the electron scale up to the fluid scale. Main research contents are: the major area of electron acceleration in the near-Earth tail, the extent and variation of dipolarization front along the dawn-dusk direction, structures and properties of electric fields around the dipolarization fronts,the essential factors determining the acceleartion efficiency at dipolarization front, the efficienty of Betatron and Fermi acceleration, wave-particle interactions at the dipolarization front etc.

对地球磁尾高能电子产生机制的研究，有助于我们理解磁层能量释放和传输过程，以及内磁层特别是辐射带中高能电子的来源，对于空间天气的预报和研究有重要意义。磁尾磁场重联被认为是近磁尾高能电子的主要来源，但是狭小的扩散区能否提供大量电子的加速存在疑问。而最近的一系列研究表明，伴随重联的电子加速可能主要发生在远离扩散区的下游高速流中。伴随高速流的偶极化锋面常常对应着高能电子通量的增强。本项目拟以Cluster和THEMIS卫星为主的多卫星观测，结合全粒子模拟和大尺度试验粒子模拟手段，揭示高速流中伴随偶极化锋面的能量释放和传输机制，涉及从电子尺度到流体尺度的多尺度物理过程。主要研究内容包括：近磁尾发生电子加速的主要区域，偶极化锋面沿晨昏方向的尺度和变化，锋面附近的电场结构和特征，锋面的哪些参数决定了电子加速效率，Betatron和Fermi加速机制的效率，锋面处的波粒相互作用过程等。