NONLINEAR INSTABILITIES IN THE NEAR-EARTH PLASMA SHEET - A 2-DIMENSIONAL MODEL WITH AND WITHOUT NEAR-EARTH FIELD LINE FLARING

We present results of two-dimensional MHD-simulations considering onse t and evolution of nonlinear resistive instabilities in the near-Earth plasma sheet. We use start configurations with and without local flar ing which describe the near-earth plasma sheet including the Earth's d ipole field explicitly. These equilibria are linearly stable against l arge scale tearing instability. This allows to study non-linear instab ilities which are not found in usual tail simulations including both p lasma sheet and lobe. These instabilities and the corresponding magnet ic reconnection occur after a phase of slow diffusive evolution. The c orresponding plasma flow differs significantly from the usual flow pat tern of a large scale tearing instability. In general, we find earthwa rd flow even tailwards of the reconnection X-line. The results show th at a near-Earth flaring of field lines can yield a significant non-lin ear destabilizing effect.