A Model of GAM intermittency near critical gradient in toroidal plasmas

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

We have constructed a four-field minimum model that describes the growing intermittency of turbulence associated with the geodesic acoustic mode (GAM) observed in our toroidal Landau-fluid simulations. The intermittent dynamics are well reproduced by the model for the reference parameters used in the simulation. The model can also reproduce more nature of turbulent transport associated with the GAM, such as a single burst leading to a full quench of turbulence and also a steady state turbulence mixed with steady state zonal flows and GAMs. Investigating the behaviour of the solution trajectories around the fixed points in four-dimensional phase space, we examine the comprehensive properties of the model and identify the bifurcation property between Dimits shift and steady state turbulence regimes, which correspond to different eigen-states.