PARTICLE SIMULATION STUDY OF COLLISIONLESS DRIVEN RECONNECTION IN A SHEARED MAGNETIC-FIELD

Nonlinear development of collisionless driven reconnection and the con sequent energy conversion process between the field and particles in a sheared magnetic field are investigated by means of a two-and-one-hal f-dimensional particle simulation. Magnetic reconnection takes place i n two steps irrespective of a longitudinal magnetic field, but the gro wth rate of the reconnection field varies in proportion to the ExB dri ft velocity at an input boundary. It is clearly observed that the trig gering mechanism of collisionless driven reconnection for the fast gro wing phase changes from an electron meandering dominance in a weak lon gitudinal field to an electron inertia dominance in a strong field. Th e electron acceleration and heating take place in the reconnection are a under the influence of reconnection electric field, while the electr on energy is converted to the ion energy through the action of an elec trostatic (ambipolar) field excited by magnetic compression in the dow nstream. It is also found that, in the presence of a longitudinal magn etic field, the electron acceleration by the reconnection field takes place effectively and the generated force-free current is maintained f or a long period while forming an asymmetric spatial profile of curren t layer. (C) 1997 American Institute of Physics.