Magnetic reconnection induced by Kelvin-Helmholtz instability
The magnetohydrodynamic reconnection induced by the Kelvin-Helmholtz instability is studied by using two-dimensional MHD equations for compressible plasma with finite resistivity. Two cases for the initial magnetic field are considered: the uniform field and the sheared field. The investigations are restricted by assumption of two-dimensional disturbances and the constant resistivity. For the Cartesian frame of reference, the simulation box composed of \(104\times 104\) grid points is used, and boundary conditions are imposed on the outer \(100\times 100\) grid points. The long time evolutions are different in the two cases: namely, the electromagnetic stress is dominant in the uniform field case, and the hydrodynamic stress is dominant in the sheared flow case. The simulations show that slow rarefaction structures which can be seen in the uniform field case, are not observed in the sheared field case. In the uniform field geometry, the magnetic field lines are twisting and reconnecting due to the Kelvin-Helmholtz instability. The magnetic reconnection reorganizes magnetic field lines so that the final configuration consists of straight field lines and is similar to the initial one, but the magnetic field strength is not uniform and the velocity shear scale length is much larger than in the initial field. In the sheared field case, no drastic changes are observed, and sheared magnetic field reconnection operates until the end of the simulation, together with the conversion of the flow energy into the thermal one. The authors show that the growth rate monotonically increases as the Alfvén Mach number \((\text{M}_{\text{A}})\) increases, and monotonically decreases as the sonic Mach number increases (if the sonic Mach number is larger than \(0.2\)). The growth rate becomes saturated when \(\text{M}_{\text{A}}>5\).
scientific article; zbMATH DE number 1071625