Stochastic magnetic field lines diffusion in a toroidal configuration (Tokamak)

In this paper, the stochastic magnetic field lines diffusion is studied. The stochastic behavior of the magnetic field lines is described by the generalized mapping to the second order which is derived from the magnetic field lines equations. The diffusion coefficient is calculated analytically using the Fourier paths technique and the characteristic function formalism. Both, they give exactly the same result of the diffusion coefficient. A numerical determination of the diffusion coefficient is also done