Statistical investigation of transport barrier effects produced by biasing in a nonfusion magnetoplasma

The effects of a biasing potential on the statistical properties of the fluctuating flux, particle density and radial velocity time series in the nonfusion magnetoplasma Thorello [C. Riccardi, D. Xuantong, M. Salierno, L. Gamberale, and M. Fontanesi, Phys. Plasmas 4, 3749 (1997)] are studied. The shape evolution of the probability distribution function (PDF) of the temporal coarse-grained fluctuating flux is investigated as a function of the radial position in the plasma equatorial plane, for different values of the bias potential applied to a limiter. A reduction of cross correlations between density and radial velocity, concomitant with an increase in the shearing rate of the radial electric field, is found near the center of the plane as a function of the bias potential. The partial density-velocity cross correlations, evaluated at different time scales, reach their asymptotic values for times of the order of those describing the change in shape of the fluctuating flux PDF. The magnitude of the shearing rate of the radial electric field, calculated at different radial positions in the plane, is consistent with the expected decorrelation mechanism of turbulent transport. (C) 2004 American Institute of Physics.