[en] Collisionless tearing modes and the enhanced transport associated with this instability are investigated theoretically and by using a two-and-one-half dimensional particle simulation code in a slab geometry. The effects of electrostatic fields on the instability are also considered. The initial current is found to diffuse along the perturbed magnetic field lines with the observed diffusion coefficient in good agreement with the theoretical prediction. Electrostatic effects have a tendency to enhance the tearing mode growth rate. The growth of the mode is observed to divide into three phases. In multi-mode tearing, a combination of magnetic islands is observed. (author)