RADIAL PROPAGATION OF TURBULENCE IN TOKAMAKS

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