Scaling of field‐line random walk in model solar wind fluctuations

The diffusion coefficient associated with random walk of magnetic field lines is computed by direct calculation of a large number of field lines from a specified statistical ensemble. Two‐component magnetic field models are examined, consisting of a mixture of slab and two‐dimensional fluctuations. The scaling of the diffusion coefficient with magnetic field strength is established numerically for a wide range of relative fluctuation amplitudes ( δb/B 0 ). The results confirm the recent nonperturbative theory of field line random walk ( Phys. Rev. Lett., 75, 2136, 1995), but depart considerably from the quasilinear B 0 −2 scaling, for models thought to be appropriate to the solar wind.