Numerical study of asymmetric driven reconnection at dayside magnetopause

A two-dimensional compressible MHD code has been used to numerically study the asymmetric driven reconnection processes in the vicinity of the magneto pause. The initial magnetic field configuration is assumed to be in a mecha nical equilibrium state. The cases with identical temperatures (T-mo/T-so=1 .0) and four different ratios of magnetic field strength (Q = B-mo/B-so = 1 .0, 1.5, 2.0, 2.5), and the case with T-mo/T-so = 2.0 and Q=1.5 are investi gated (B-mo, T-mo and B-so T-so are the initial magnetic strength and tempe rature outside the current sheet on the magnetosphere and the magnetosheath , respectively). When the magnetic field on the magnetosheath side is set a s southward, a recurrent formation of multiple magnetic bubbles with variou s scales occurs under the action of the inward plasma flow imposed at the l eft and right boundaries. In the simulation, some bubbles coalesce into a b igger one and then it is convected out of the simulation domain; the others are convected through the top boundary all alone. Thus, the plasmoid event s with different scales and different time intervals take place intermitten tly and the impulsive features of magnetic reconnection are clearly shown. The multiple magnetic islands are all high-temperature and large-density re gions in comparison with the ambient environment. The bipolar signatures or fluctuant variations of normal magnetic field component are generated by t he formation of multiple magnetic islands. This result is similar to the FT Es signature.