Effective diffusion and nonlocal heat transport in a stochastic magnetic field

Heat transport in a stochastic magnetic-field configuration is investigated analytically and numerically with two complementary models: a Chirikov-Taylor map model and a Gaussian random-field model. Numerical solution of the Chirikov-Taylor model shows a short-time nonlocal regime, but at large time the Rechester-Rosenbluth effective diffusion regime is confirmed numerically. The Gaussian model, for which the associated nonlocal propagator is calculated, describes this short-time behavior.