ON CURRENT SHEETS IN 2-DIMENSIONAL IDEAL MAGNETOHYDRODYNAMICS CAUSED BY PRESSURE PERTURBATIONS

In this paper it is shown that in ideal magnetohydrodynamics (IMHD) a two-dimensional equilibrium with an X-shaped neutral point (X-point) c onfiguration reacts to small and smooth perturbations of the plasma pr essure by the development of sheets with singular current density whil e the X-point structure is replaced by a different kind of configurati on containing either cusp-like or T-shaped singularities. This behavio r is demonstrated by computing the time dependent response to a suitab le initial perturbation using a relaxation method within ideal MHD. Th e two-dimensional configurations considered in this paper are motivate d by models of space plasma systems like, e.g. the Earth's magnetotail containing a distant X-point where perturbations caused by the solar wind may force the formation of current sheets and the subsequent occu rrence of magnetic reconnection.