Computer Simulation of the Three-dimensionsal De- Cay of Thin Collisionless Current Sheets

Recent theoretical investigations and simulations of collisionless space plasma current sheets have claimed their stabilisation against reconnection by nite cross-sheet magnetic eld components. However, all these theoretical investigations and simulations were based on two-dimensional models. Currrently we have shown that the energy variations change quite a bit as soon as one considers the problem in three dimensions { the sheet can become unstable in three dimensions where it was stable in two dimensions. Since it is di cult, however, to evaluate the three-dimensional structure of the dynamical current sheet decay analytically, numerical simulations will be helpful. Here in this paper we report results of our numerical simulations of the three-dimensional decay of a thin Harris current sheet. We demonstrate that in three dimensions the decay of a thin collisionless current sheet starts with the unstable growth of a compressional sausage-mode wave, propagating in the current direction. Afterwards reconnection begins at a time scale faster than a tearing mode instability known from the past two-dimensional considerations.