Onset and saturation of guide-field magnetic reconnection

The onset and saturation of collisionless magnetic reconnection in the presence of a guide field are investigated using two-dimensional particle-in-cell simulations in which the reconnection evolves out of the initial thermal noise in the current sheet and in which the resolution is sufficient to resolve the electron singular layer. The simulations show that reconnection does not abate when the island width exceeds either the electron singular layer or the initial current sheet width. Instead, reconnection proceeds through an explosive stage which appears to be limited only by the spatial size of the system. The guide-field reconnection dynamics is dominated by the formation of an asymmetric configuration with a deep density cavity along one pair of separatrix arms. In this cavity an electron beam feature is formed which excites the Buneman instability. Near the X line the reconnection electric field is supported by a combination of quasiviscous and bulk inertia effects for the electrons. Around the island perimeter, intense Debye-scale, predominantly perpendicular, electric field structures are formed. (C) 2005 American Institute of Physics.