A Two-dimensional Hybrid Simulation Study Of The Magnetotail Reconnection

The process of magnetic reconnection and ion dynamics in the distant magnetotail are studied by using a two-dimensional three components (2.5D) hybrid simulation. The simulation domain is a rectangle in the xz plane around X line in the distant magnetotail. An initial current sheet separates the simulation domain with antiparallel magnetic field components in the x direction. A finite resistivity is imposed at the center of the simulation domain and the collision frequency is used to model the resistivity. It can be found that a leading bulge-like magnetic field configuration is formed during the process of magnetic reconnection. The magnetic field decreases and plasma flow speed, temperature, density, thermal pressure increase from either lobe region to the plasma sheet center. A strong temperature anisotropy is found in the plasma sheet boundary layer. The research indicates that although the guide field is taken to be zero, the B_y contours show a clear quadrupolarstructure around the X point. In addition, the velocity distributions of ion deviate from the initial Maxwell distribution in the outflow region.In the first chapter, a brief introduction of the concept and process, classical physical model and the research general situation of magnetic reconnection in space plasma is made.The advantages and disadvantages between the MHD simulation method, full particle simulation method and hybrid simulation method are compared in the second chapter. Then a brief introduction of the hybrid simulation method is made.In the third chapter, the simulation model, basic equations, normalized parameter, initial conditions and boundary conditions are presented. This section also describes the particle and magnetic field update.The simulation results and discussions are presented in the fourth chapter. The structures of magnetic field and the evolutions of some physical quantities have been shown. The quadrupolar structure of B_y is also shown. The temperature anisotropy and the iondistribution in the outflow region are discussed in this section also.Finally, conclusions and the future work are given in the last chapter.