Radial propagation of turbulence in tokamaks

It is shown that turbulence propagation can be due to toroidal or non-linear mode coupling. An analytical analysis indicates that the toroidal coupling acts through convection while the non-linear effects induce diffusion. Numerical simulations suggest that the toroidal propagation is usually the faster process, except perhaps in some highly turbulent regimes. A consequence is the possibility of non-local effects on the fluctuation level and the associated transport