Experimental Evidence of Self-Regulation of Fluctuations by Time-Varying Flows

We report the first extended experimental results indicating that radially localized time-varying potential structures, which possess many of the characteristics of zonal flows, are generated by strong fluctuations. Experiments performed in the H-1 heliac show that these poloidally symmetric flows are nonlinearly coupled to other fluctuations and are responsible for significant modifications in fluctuations and in the fluctuation-driven transport.