Perpendicular diffusion in magnetostatic slab turbulence: The theorem on reduced dimensionality and microscopic diffusion

In the present paper we revisit the problem of perpendicular diffusion in magnetostatic slab turbulence. It is shown that the particles cannot be scattered away from the magnetic field line by more than an unperturbed Larmor radius. This result confirms the theorem on reduced dimensionality proposed earlier for this special case. Furthermore, we estimate the motion of the particles away from the field line often called microscopic diffusion. The relation between the microscopic diffusion coefficient derived in the present paper and well-known results such as classical scattering theory and Bohm diffusion is also discussed.

► I prove the theorem on reduced dimensionality for slab turbulence.
► The motion of energetic particles away from the magnetic fields lines is discussed.
► The latter results are compared with previous results of diffusion theory.