Plasma diffusion in the presence of waves

Diffusion in plasma is considered with the help of the moment equations. If low-frequency waves are present which move the ions, diffusion can arise due to non-linearly saturated waves which cause an energy transfer from electrons to ions, or also due to growing waves. Already in weak turbulence the order may exceed the classical diffusion, e.g. for resistive drift waves.In slab geometry the diffusion (or the anomalous resistance) depends in the case of electrostatic waves on the Coulomb force ni E⊥, ni being the ion perturbation and E⊥ the electric field of the waves perpendicular to the density gradient and to the magnetic field. In an axisymmetric torus the diffusion is changed essentially by a factor (1+⋅/⋅⊥), since electric fields parallel to the magnetic field contribute.