Infoscience

Conference paper

Global gyrokinetic simulations of rho* and nu* scalings of turbulent transport

Turbulent transport dynamics and level are investigated with the 5D gyrokinetic global code GYSELA, modelling the Ion Temperature Gradient instability with adiabatic electrons. The heat transport exhibits large scale events, propagating radially in both directions at velocities of the order of the diamagnetic velocity. The effective diffusivity is in agreement with that reported in other gyrokinetic codes such as ORB5. Transition from Bohm to gyroBohm scaling is observed on the turbulence correlation length and time, when the normalized gyroradius $\rho_*$ is decreased from $10^{-2}$ to $5 \cdot 10^{-3}$. The transition value could depend on the distance to the ITG threshold. Collisions are modelled by a reduced Lorentz-type operator. It allows one to recover theoretical neoclassical predictions in the banana and plateau regimes, namely the heat diffusivity and the mean poloidal flow. In the turbulent regime, preliminary results suggest the turbulent transport increases with collisionality close to the threshold, in agreement with previous publications. Finally, the mean poloidal flow can be increased by about 40% as compared to the neoclassical value.

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