Hybrid Simulation Studies For Profile Effect Of Shear Flows On The Magnetic Reconnection

Magnetic reconnection plays important roles in space and laboratory plasma researches, as it is the key event for many phenomena in space and magnetic confinement fusion plasmas. When the magnetic reconnection occurs, the magnetic field topology is changed, the magnetic energy is transformed to the plasma kinetic energy and thermal energy, the high-speed plasma flow is produced. The theories of magnetic reconnection are always improved since it was brought out, because this issue is very complicated and the observation of space and laboratory plasmas is also limited. Hence there are still debates on some important events. Since the instability with shear flows in the steady state equilibrium cannot be solved based on the energy principle method, the present research has to be limited to the solution of initial value problems and to the static state equilibrium.The shear flows are inevitably generated in the complicated space environments and thereby have great effects on the reconnection process. In this work, therefore, we used a two-dimensional hybrid model with three components to investigate the effects of the shear flows on the collisionless magnetic reconnection. It is found that in the magnetic reconnection process, the magnetic field topology is changed obviously and the magnetic field lines become curved strongly. In the outflow region, moreover, the magnetic field strength decreases as well as the plasma flow speed, temperature, density and thermal pressure increase. The Hall current is produced the X point of the magnetic island due to the different dynamic behaviors of ions and electrons. A quadrupole structure of magnetic field components vertical to the reconnection plane is also induced. When the shear flows are imposed into the reconnection process, the increase of the flow shear or the decrease of the flow layer width clearly reduces the saturated island widths. It is also observed that the shear flow reduces the maximal reconnection rate in the nonlinear evolution of magnetic reconnection, which indicates that such a shear flow can significantly suppress the trigger of fast magnetic reconnection. In addition, it is found that the shear flows can notably change the quadrupole structure of magnetic field components, which no doubt affects the observation and predication of the fast magnetic reconnection.