Influences Of The Shear Flow On Formation Of Slow Shocks And Its Structure In Tearing Mode Instability

Magnetic reconnection associated with the change of magnetic field topology is an important process to convert magnetic energy into plasma kinetic and plasma thermal energies, which has been used to explain many natural phenomena of the sudden release of energy. Magnetic reconnection is often triggered by the tearing mode instability. Shear flow is ubiquitous in both space and laboratory plasmas and has a major impact in some instabilities such as the tearing mode. Shocks are commonly observed in geophysical and laboratory plasmas. The value and direction of physical variables can be changed sharply between the upstream and downstream of shocks.In this thesis, numerical simulation is carried out to study the sub-Alfvenic shear flow influence on tearing mode stability. Based on the compressible resistive MHD model and the compressible Hall MHD model, we investigate the formation of the shock and its structures outside the reconnection layer in the presence of sub-Alfvenic shear flow.From the compressible resistive MHD model, it is. found that two pairs and one pair of slow shocks are formed outside the reconnection layer for plasma betaβ=0.2 andβ=1.0, respectively. However, for the case with a higher plasma betaβ=5.0, no shock is formed outside the reconnection layer. It is believed that the mechanism of the formation of these slow shocks is associated with the interaction between the initial imposed shear flow and the plasma flows generated by magnetic reconnection. In the Hall MHD model, there are also structures formed outside the reconnection layer, but they can not be simply classified as a simple MHD discontinuity. Usually, they are mixed structures of some MHD discontinuities. The whistler wave introduced by the Hall effect is a dispersive wave which affects the formation of the discontinuity. As a result, the layer structure of the discontinuity becomes a wave train with the increase of ion inertial length dj. As the ion inertial length dj increase, the wave train becomes broader and the number of oscillation periods in the wave train are reduced.