STOCHASTIC DIFFUSION OF MAGNETIC-FIELD LINES

A renormalized diffusion coefficient for magnetic field lines is presented by using the renormalized weak turbulence theory. It is defined on locally destroyed magnetic surfaces caused by two tearing modes. The renormalized diffusion coefficient is given in terms of a renormalized propagator expressed by the integral of the Bessel function of the first kind, J1. It is free from delta-function-type divergence. An averaged renormalized propagator is introduced whose imaginary part represents the behaviour of the memory of the initial condition. Numerical calculation shows that the averaged propagator decreases within a correlation damping time.