Observations and Simulations of Magnetic Fluctuations in MCX

Abstract

Recently magnetic fluctuations in the Maryland centrifugal experiment (MCX) have been measured by an azimuthal array of 16 probes in the edge region of the plasma. A detailed analysis indicates that there is primarily a convection of m = 2 fluctuations by the azimuthally rotating plasma. However, the frequency spectrum of this mode is broad and is almost of the same order as the frequency. Furthermore, bicoherence analysis indicates dominant nonlinear interaction between m = 2 and a low frequency m = 0 mode. We utilize a 2D MHD code to investigate the dynamics of the primary interchange instability. For very low sheared rotation there is a broad spectrum (in m) of unstable modes. However, as the sheared rotation is increased the high mode numbers become stabilized. We will present detailed comparisons of spatio-temporal dynamics of our simulations with the data from the magnetic probes.