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Via nonlinear gyrokinetic simulations, microturbulent transport is investigated for electromagnetic trapped electron mode (TEM) and ion temperature gradient (ITG) tokamak core turbulence with β up to and beyond the kinetic ballooning mode threshold. Deviations from linear expectations are explained by zonal flow activity in the TEM case. For the ITG scenario, β-induced changes are observed in the nonlinear critical gradient upshift—from a certain β, a strong increase is observed in the Dimits shift. Additionally, a Rechester–Rosenbluth-type model for magnetic transport is applied, and the amplitudes of magnetic field fluctuations are quantified for different types of turbulence.
Pueschel et al. (Tue,) studied this question.