Zonal flows and transport in ITG turbulence
Sheikh Dastgeer, Sangeeta Mahajan* and
Department of Electromagnetics, Chalmers University of Technology &
Euratom-VR Association, S-412 96 Göteborg, Sweden
*Center for Plasma Theory and Computation, USA
Nonlinear fluid simulations of self interactive ion temperature gradient (ITG) modes in magnetically confined fusion plasmas, using a reactive fluid closure, exhibit generation of zonal flows. These have been found to inhibit ion heat transport significantly up to certain critical level approximately equal to the nonlinear Dimit's upshift. These flows also cause the damping of long wavelength eddies present in the turbulence. Our simulation results have been in fairly good agreement with the earlier analysis of advanced reactive fluid model, based upon reductive perturbation method, that demonstrates resonant excitation of the zonal flows close to linear marginal stability of the ITG mode. The magnitude of ion heat diffusivity in our numerical simulation as well as analytical work agree reasonably well with the results presented in the cyclone simulation work.