RECONNECTION IN THE NEAR-EARTH PLASMA SHEET - A 3-DIMENSIONAL MODEL

We present results of three-dimensional MHD simulations of reconnectio n in the near-Earth plasma sheet. We use two-dimensional start configu rations which include the Earth's dipole field explicitly and three-di mensional resistivity profiles. These equilibria are stable against la rge-scale tearing instability, that is, the mode with the maximum grow th rate. For nonhomogeneous resistivity profiles, however, the system may become unstable against nonlinear, resistive modes. We discuss ons et and nonlinear evolution of reconnection due to these instabilities. One result of our three-dimensional simulations is that earthward flo w can be found even tailward of the reconnection region. This confirms a typical feature of previous two-dimensional simulations of reconnec tion in the near-Earth plasma sheet. The nonlinear resistive instabili ties found in our simulations could be relevant for phenomena like pse udobreakups.