Influence of magnetic shear and stochastic electrostatic field on the electron diffusion

The electron diffusion induced by a two-dimensional electrostatic turbulence, in a sheared slab approximation of the toroidal magnetic geometry, is studied by direct numerical simulation. The transport properties of the electrons are obtained by numerical simulations assuming an isotropic spectrum of electrostatic drift type turbulence that is Gaussian for small wavevectors and power-law k-3 for large wave-vectors. The 'radial' and the 'poloidal' running and asymptotic diffusion coefficients of electrons are obtained for physically relevant parameter values and the existence of an enhanced diffusion in the poloidal direction is observed in the presence of magnetic shear. (authors)