Interaction among different spatio-temporal scale fluctuations through zonal flows
Y. Kishimoto,1 J.Q. Li,1 Y. Idomura,1 A.I. Smolyakov 1,2
1 Naka Fusion Research Establishment, JAERI, Naka, Ibaraki, 311-01 Japan
2 University of Saskatchewan, Saskatoon, S7N 5E2 Canada
Abstract.
Zonal flows generated by fluctuations on some scale are expected to affect fluctuations on other different scales in addition to regulating their own fluctuation level. Demonstrating a new role of the zonal flow, we present new intermittent (and/or bursting) transport dynamics resulting from the interaction among different spatio-temporal scale fluctuations through zonal flows. As an example, here we discuss ITG turbulence embedded in a small scale ETG-driven zonal flow based on 3-dimensional gyro-fluid simulations. We have found a new suppression mechanism of the long wavelength ITG mode by the small-scale ETG-driven zonal flow. The origin is from the radial non-local mode coupling and the associated energy transfer between unstable long wavelength ITG modes and near marginal (and/or stable) short wavelength modes through zonal flow. Besides the role of suppression of ITG turbulence, we have for the first time observed intermittent and/or bursting behavior in the ion heat transport originating from the complicated mutual interaction among ETG-driven zonal flows, ITG turbulence, and the associated ITG-driven zonal flows.