(TH/P8-18) New Characteristics of Zonal Flows in Multi-scale Plasma Turbulence

J.Q. Li1), K. Uzawa3), Y. Kishimoto1), Y. Kouduki1), Z.X. Wang1)
 
1) Kyoto University, Uji, Kyoto, Japan
2) Institute for Fusion Theory and Simulation, Zhejiang University, Hangzhou, China
3) National Institute for Fusion Science, Toki 509-5292, Japan

Abstract.  The nonlinear interaction in multi-scale plasma turbulence including resistive kink-tearing mode (RKTM) and ion temperature gradient (ITG) mode is studied based on a 5-field gyrofluid simulation aiming to understand the underlying physical mechanisms. We discuss specifically the zonal flow( ZF) dynamics in mixed MHD and ion-scale turbulence as well as the dual stabilization effects. Here we report two new findings on the ZF characteristics: (1) A robust oscillatory ZF with finite frequency in mixed MHD and ITG turbulence is created due to the multi-scale interaction so that the ion heat transport is not efficiently suppressed. This implies probable degeneration of the favorable role of ITG ZFs by MHD fluctuations. (2) A coupled ZF eigenmode is found in Hasegawa-Mima (HM) model due to the radial spectral effect of ZFs, where all components have the same enhanced growth rate. It is identified that this new eigenmode originates from successive cross coupling between ZFs and turbulent sidebands.

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