On the transition to drift turbulence in a magnetized plasma column

Abstract

Experimental results from a magnetized argon plasma column demonstrate a controlled transition to a turbulent state as the magnetic field (B) strength is increased. At lower B there is an onset of fluctuations in density and potential. These are shown to be due to drift waves that have been modified by flow shear. As B is increased the character of the fluctuations undergoes several changes. These changes include a general decrease of coherence, an increase in the phase lag (between density and potential), and a straightening of the observed dispersion relation. Concomitantly, the intensifying and broadening fluctuation spectra lead to significant cross-field radial particle transport. Other nonlinear dynamical activity is inferred during the transition, e.g., three-wave interactions, the formation of localized structures (that do not significantly contribute to the net particle transport), and energy transfer to the largest available scales.