Study of driven magnetic reconnection in a laboratory plasma

The magnetic reconnection experiment has been constructed to investigate the fundamental physics of magnetic reconnection in a well-controlled laboratory setting, This device creates an environment satisfying the criteria for a magnetohydrodynamic plasma (S much greater than 1, (rho i) much less than L) The boundary conditions can be controlled externally, and experiments with fully three-dimensional reconnection are now possible. In the initial experiments, the effects of the third vector component of reconnecting fields have been studied, Two distinctively different shapes of neutral sheet current layers, depending on the third component, are identified during driven magnetic reconnection. Without the third component (antiparallel or null-helicity reconnection), a thin double-Y-shaped diffusion region is identified, A neutral sheet current profile is measured accurately to be as narrow as the order of the ion gyroradius. In the presence of an appreciable third component (co-helicity reconnection), an O-shaped diffusion region appears and grows into a spheromak configuration. (C) 1997 American Institute of Physics.