Coherent to turbulence transition, enhanced flow and confinement in a simple toroidal plasma

Abstract

In a simple toroidal plasma, self consistent poloidal flow generation at different toroidal fields is observed. On changing the magnitude of toroidal field, transition occurs in the nature of fluctuation from highly coherent modes at low magnetic field to a turbulent broadband spectrum at high field accompanied by significant improvement in the confinement. Interestingly, though the coherence is reduced with the increasing field, the fluctuation driven poloidal flux remains comparable. The observed increase in the densities on high field side with the increase in magnetic field is simultaneously accompanied by the enhanced net poloidal flow. The present work demonstrates that in a toroidal compressible plasma, an intimate relationship exists between the fluctuations, self consistently generated flows and enhanced confinement.