A Resistive MHD Simulation of the Shear Flow Effects on the Structure of Reconnection Layer

Abstract

By using a one-dimensional resistive magnetohydrodynamic (MHD)model, the Riemann problem is solved numerically for the structureof the reconnection layer under a sheared flow along theanti-parallel magnetic field components. The simulation is carriedout for general cases with symmetric or asymmetric plasma densitiesand magnetic fields on the two sides of the initial current sheet,and cases with or without a guide magnetic field, as in variousspace and fusion plasmas. The generation of MHD discontinuities inthe reconnection layer is discussed, including time-dependentintermediate shocks, intermediate shocks, slow shocks, slowexpansion waves, and the contact discontinuity. It is shown that thestructure of the reconnection layer is significantly affected by thepresence of the shear flow. For an initial symmetric current sheet,the symmetry condition is altered due to the shear flow. For caseswith an asymmetric initial current sheet, as at the Earth'smagnetopause, the strengths of MHD discontinuities changesignificantly with the shear flow speed. Moreover, the generalresults for the reconnection layers in the outflow regions on eitherside of the X line are discussed systematically for the first time.