On current sheets in two-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) configuration reacts to small and smooth perturbations of the plasma pressure by the development of sheets with singular current density while the X-point structure is replaced by a different kind of configuration containing either cusp-like or T-shaped singularities. This behavior is demonstrated by computing the time dependent response to a suitable initial perturbation using a relaxation method within ideal MHD. The two-dimensional configurations considered in this paper are motivated 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 occurrence of magnetic reconnection