Present Status and Prospects of Research on Zonal Flow 3.Recent Experimental Studies of Zonal Flow 3.1 Study of Zonal Flow by Fluctuation Diagnostics

Abstract

Zonal flows are now widely recognized to be a key phenomenon for understanding of fluctuation-induced transport in magnetically confined plasmas. The existence of the zonal flows has been directly identified by the measurement of electric-field fluctuations as well as of bicoherence of drift-wave turbulence which introduces the energy transfer from drift waves to zonal flows via three-wave interactions. The appropriate diagnostic methods for these subjects are introduced.