On the transition to drift turbulence in a magnetized plasma column

TLDR

The transition is driven by drift waves modified by flow shear. Increasing the magnetic field induces a controlled shift from coherent fluctuations to turbulent drift‑wave activity, reducing coherence, increasing phase lag, straightening the dispersion relation, broadening spectra, and enhancing cross‑field particle transport while generating nonlinear interactions and large‑scale energy transfer.

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.