Fast Camera Images of Flux Ropes During Plasma Relaxation

Abstract-Images of visible light emission from flux ropes during plasma relaxation are presented. Multiple images are used to gain insight into the dynamics of driven/dissipative plasma relaxation processes in finite-? plasmas. A fast-gated (40-200 ns) intensified charge coupled device (ICCD) camera generates time-resolved images of 1-3 flux ropes in the reconnection scaling experiment (RSX) device. During relaxation, flux ropes are observed to evolve toward states characterized by the presence of single and multiple helical mode structures. Index Terms-Cylindrical, dissipation, flux ropes, helicity, instability, mode structures, relaxation.

Plasma relaxation, the tendency of plasmas to evolve toward a preferred equilibrium state determined by global constraints, is a topic of interest in both laboratory and astrophysical plasmas. The Taylor relaxation paradigm [1], while successful in predicting equilibrium plasma states such as spheromaks and reversed field pinches, can be rigorously applied only to zero ?, nondriven plasmas in the absence of flows. Such stringent limitations can be overcome by different approaches such as the minimum dissipation rate theory [2], which has yet to be tested experimentally. Our research is geared toward providing dedicated experiments to investigate the effects of nonnegligible plasma flow, finite/high ?, and external drive on plasma relaxation.