Abstract
Abstract
Zonal flows are m = n = 0 electrostatic potential fluctuations with a finite radial wave-number. Plasma shaping effects on zonal flow are studied with gyrokinetic theory. We focus on the effect of the elongation E particularly. A new coordinates which are related to elongation are rigorously developed in the analysis of gyrokinetic equation. The GAM real frequency and damping rates are inversely proportional to elongation E which seems to be consistent with that measured in ASDEX-Upgrade. The lower the GAM frequency the more important it is expected to become in moderating the turbulence via shear decorrelation. Reduction of GAM damping rates could help to generate the zonal flow.
Subject
General Physics and Astronomy