EFFECTS OF STOCHASTIC DRIFTS AND TIME-VARIATION ON PARTICLE DIFFUSIONIN MAGNETIC TURBULENCE

The effect on the guiding center trajectories of the stochastic drifts due to the curvature of the stochastic magnetic lines is studied in t he first part of this paper. It is shown that the subdiffusive root t behavior of the mean square displacement of the particles cannot exist in a realistic magnetic configuration. The particles undergo a diffus ive process even in the absence of the perpendicular collisional diffu sion. The anomalous diffusion coefficient is estimated. The second par t of this work deals with time-dependent stochastic perturbations of t he confining magnetic field. It is shown that the time variation has a strong effect of decorrelating the particles from the magnetic lines. The diffusion coefficient is determined as a function of the correlat ion time of the stochastic field. The influence of a cross field colli sional diffusion on the results of the two problems presented here is also estimated.