New Regimes of Magnetic Reconnection in Collisionless Plasmas

An implicit particle-in-cell code has been used to study collisionless magnetic reconnection of a current sheet. The reconnection process is found to occur in three distinct stages: (1) early spontaneous reconnection fed by the free energy of an initial anisotropy in the electron component; (2) coalescence of the resulting small-scale filaments of electron current, accompanied by electron jetting; and (3) oscillatory flow of electrons through the magnetic $X$ point, superposed on continuing nonlinear growth of ionmediated reconneciton. The time evolution of stage 3 is strongly dependent on $\frac{M_i}{m_e}$.