Strong plasma turbulence and anomalous diffusion in a magnetic field

Plasma diffusion in the presence of strong turbulence has been studied by means of analytic theory and numerical simulations. First, diffusion and turbulent fluctuation spectra in the presence of convective cells are studied using a two-dimensional guiding center model and a two-fluid model retaining ion inertia. It is shown that for these models, turbulent diffusion takes place which dissipates a density gradient and is associated with the inverse cascades of the fluctuations transferring the electric field energy toward the long wavelength modes. Second, particle diffusion associated with drift wave turbulence using full dynamic ions and Debye shielding electrons is considered. It is shown that diffusion and the inverse cascades are much slower in this model compared with those found for convective cell turbulence. This difference arises from the fact that the mode coupling coefficient for inverse cascade is much smaller for the drift wave turbulence compared with the turbulence associated with the convective cells.