NONLINEAR SIMULATION OF TURBULENT FIELD LINES AND COMPARISON OF THEIR MEAN CROSS-FIELD DISPLACEMENT WITH THEORETICAL PREDICTION

A new method for the full nonlinear computation of turbulent field lines is presented that extends the Sums of Random Numbers Distribution method previously applied to the computation of generalized quasilinear (GQL) field lines. A study of the mean cross-field displacement confirms the theoretical prediction of a nonlinear diffusion regime, on the large scales where the mean cross-field displacement exceeds twice the perpendicular correlation length. The simulation results duplicate at all length scales the variations of the mean cross-field displacement predicted by the theoretical calculations, including the transitions from GQL supradiffusion to nonlinear diffusion. Both GQL and full nonlinear computations also reproduce, accurately, the predicted variations with turbulence level of the large-scale GQL and nonlinear diffusion coefficients, respectively.