Excitation of Zonal Flows by Ion temperature gradient Modes excited by the Fluid Resonance

Artikel i vetenskaplig tidskrift, 2015

We apply the Reductive perturbation method to the simple electrostatic ITG mode in an advanced fluid description. The fluid resonance turns out to play a dominant role for the excitation of zonal flows. This is the mechanism recently found to lead to the L-H transition and to the nonlinear Dimit’s upshift. It is important that we have here taken the nonlinear temperature dynamics from the Reynolds stress as the convected diamagnetic flow. This has turned out to be the most relevant effect as found in transport siumulations of the L-H transition, internal transport barriers and Dimits shift. This is the first time that an analytical method is applied to a system which numerically has been found to give the right experimental dynamics.