NEOCLASSICAL DIFFUSION IN A TURBULENT-PLASMA

The authors study a new diffusion mechanism which is observed when ele ctrostatic fluctuations and toroidal drift are taken into account simu ltaneously. The diffusion is caused by transitions of particles from t rajectories localized in the convective cells of electromagnetic fluct uations to trajectories aligned in the direction of toroidal drift. Th e spatial transport coefficient is found to be comparable to or higher than neoclassical diffusion in the plateau regime, regardless of the collision frequency, and is only weakly dependent on the parameters of the fluctuation spectrum for upsilon greater-than-or-equal-to u(d).