SIMULATION OF THE KELVIN-HELMHOLTZ INSTABILITY IN THE MAGNETIZED SLABJET

Two-dimensional magnetohydrodynamic simulations are performed to study the evolution of the Kelvin-Helmholtz instability for a slab jet movi ng parallel to the magnetic field. Surface waves are excited at each o f the side boundaries, and the time evolution of the individual mode, as well as its interaction with the mode excited at the opposite bound ary, is observed. The instability is very disruptive when the excited perturbations on the two side boundaries are antisymmetric. The long-t erm evolution of the antisymmetric perturbation shows a kinklike magne tic held structure after multiple reconnection events, while the symme tric perturbation yields wavy signatures only around the jet boundarie s. Three different cases of the thin slab jet are considered with the antisymmetric perturbation: a hydrodynamic jet, a jet embedded in a un iform magnetic held, and a thermally confined magnetized jet. Although the imposed magnetic fields are weak, they show quite different evolu tions. In the hydrodynamic case, the density and how patterns associat ed with the vortices survive until the end of the simulation without s ignificant changes after the initial development of the instability. F or the jet embedded in a uniform magnetic field, the density pattern a ssociated with the vortex is destroyed as magnetic reconnection develo ps, and a steady increase in density from the central jet region towar d the side boundaries is seen at the final stage when the magnetic fie ld becomes hat again. The density and flow structures in the thermally confined magnetized jet are similar to those of the hydrodynamic case , but they change slowly with the evolution of the magnetic field. Als o, it is seen that the magnetic fields that originally reside in the j et are expelled out to the side boundaries. Similar results are obtain ed for both the transonic jet and the supersonic jet, but the density variation is more significant in the supersonic case.