Studies of magnetic reconnection in a laboratory plasma

Abstract

Summary form only given. Magnetic reconnection is an ubiquitous process in space and the laboratory, causing topological change, acceleration and heating in ideal plasmas. Reconnection plays a lead role in the interaction of the solar wind with the magnetosphere and also in the dynamics of magnetic field in the solar corona. The conversion of magnetic energy to plasma flows and thermal energy associated with reconnection is speculated to be the cause of the energy release and coronal heating associated with solar flares. The Magnetic Reconnection eXperiment (MRX) was constructed in 1995 to study magnetic reconnection in a high-Lundqvist number (S=/spl tau//sub resistive///spl tau//sub Alfven/) plasma. The experiment has been operated in a nearly axisymmetric (2-D) reconnection geometry, and has yielded many exciting results. Formation of double-Y and O-shaped diffusion regions have been observed, depending on the presence of a third field component. The merging rate is seen to be faster in the null-helicity (no toroidal field component) configuration than in the co-helicity configuration (relatively strong background toroidal field), where O-point formation is observed. Using a high-density magnetic probe array, the width of the current sheet (/spl delta/) in MRX can be accurately measured. In the null-helicity case, the neutral sheet width is on the order of the ion gyroradius (/spl rho//sub i/) and the ion skin depth (c//spl omega//sub p,i/). Through control of the plasma density, plasmas can be created in MRX in the collisional (/spl lambda//sub e,mfp//spl lsim//spl delta/) and collisionless (/spl lambda//sub e,mfp//spl Lt//spl delta/) regimes.