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Report No.

Intermittent transport associated with the geodesic acoustic mode near the critical gradient regime

Miki, Kazuhiro*; Kishimoto, Yasuaki; Miyato, Naoaki; Li, J. Q.*

Turbulent transport near critical gradient in toroidal plasmas is studied based on global Landau-fluid simulations and an extended predator-prey theoretical model of ion temperature gradient (ITG) turbulence. A new type of intermittent transport associated with the emission and propagation of geodesic acoustic mode (GAM) is found near critical gradient regime, which is referred to GAM intermittency. The intermittency is characterized by new time scales of trigger, damping, and recursion due to GAM damping. During the recursion of intermittent bursts, stationary zonal flow increases with a slow time scale due to the accumulation of undamped residues and eventually quenches the turbulence, suggesting that a nonlinear up-shift of critical gradient, i.e. Dimits shift, is established through such a dynamical process.



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Category:Physics, Multidisciplinary



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