We examine magnetic surfaces and randomization of field lines with fluctuations transverse to a uniform magnetic field. Analogy with passive scalar transport in inviscid 2D flow provides realizations of magnetic surfaces and motivates a nonperturbative statistical approach. The stochastic wandering of magnetic field lines leads to diffusive perpendicular transport. For two-component fluctuations, appropriate for solar wind turbulence, the diffusion coefficient is a nonadditive combination of slab and 2D coefficients, approaching the latter in the small amplitude limit.

• Received 27 April 1995

DOI:https://doi.org/10.1103/PhysRevLett.75.2136