FIELD-LINE TRANSPORT IN STOCHASTIC MAGNETIC-FIELDS - PERCOLATION, LEVY FLIGHTS, AND NON-GAUSSIAN DYNAMICS

The transport of magnetic field lines is studied numerically in the case where strong three-dimensional magnetic fluctuations are superimposed to a uniform average magnetic field. The magnetic percolation of field lines between magnetic islands is found, as well as a non-Gaussian regime where the field lines exhibit Lévy random walks, changing from Lévy flights to trapped motion. Anomalous diffusion laws Δxi2sα with α>1 and α<1 are found for low fluctuation levels, while normal diffusion and Gaussian random walks are recovered for sufficiently high fluctuation levels. © 1995 The American Physical Society.