Collisionless magnetic reconnection in the presence of a guide field

The results of kinetic simulations of magnetic reconnection in Harris current sheets are analyzed. A range of guide fields is considered to study reconnection in plasmas characterized by different beta values, beta>m(e)/m(i). Both an implicit particle-in-cell (PIC) simulation method and a parallel explicit PIC code are used. Simulations with mass ratios up to the physical value are performed. The simulations show that the reconnection rate decreases with the guide field and depends weakly on the mass ratio. The off-diagonal components of the electron pressure tensor break the frozen-in condition, even in low beta plasmas. In high beta plasmas, evidence is presented that whistler waves play a key role in the fast reconnection physics, while in low beta plasmas the kinetic Alfven waves are important. The in-plane and the out-of-plane ion and electron motion are also considered, showing that they are influenced by the mass ratio and the plasma beta. (C) 2004 American Institute of Physics.