Transient Reconnection caused by the Impact and sudden Stop of Non-Homogeneous Dynamic Pressure

Abstract

It is proposed that local and transient reconnection in the plasma boundary layer can be caused by the impact and switch-off of non-homogenous dynamic pressure. The two dimensional compressible magnetohydrodynamic (MHD) simulation is used to investigate the reconnection processes in these two cases. It is found that the state of transverse flow and its lasting period play an important role in reconnection processes. When the transient flow is homogeneous, it does not causes reconnection, the magnetic field lines are only pushed downstream. When the transverse flow is sheared one, magnetic reconnection always occurs during the impacting period, and a new “reverse K” pattern reconnection configuration is formed in the current sheet region; after the external shear flow stop suddenly, the system of the plasma boundary layer becomes very unstable, many kinds of fluid vertex, flow pattern and reconnection configuration are generated in the current sheet region, the reconnection configurations are very different from that for impact phase. We suppose that the sudden stop of an external flow action may be an important trigger mechnism of energy conversion and magnetic reconnection. According to the simulation results. An alternative transient reconnection model has been proposed, it can be called “transient shear flow driven reconnection” model. This model is quite different from MXR model, VIR model and BSXR model. The reconnection mechanism proposed in this paper may be existed in some regions of space plasma, such as the subsolar point region of dayside magnetopause boundary layer. This reconnection model can be used to investigate the formation and structure of FTEs, osillation of magnetopause, vortex structure and the excitation of wave in the dayside magnetopause boundary layer.