The Kubo number as a parameter governing the level of chaos in magnetic turbulence

It is well known that the Kubo number R allows to classify the transport re gimes in turbulent systems. A small Kubo number leads to the so-called quas ilinear diffusion coefficient, while a large Kubo number corresponds to the percolative diffusion coefficient. Here we show, by means of a numerical s imulation of magnetic field line transport in a three-dimensional anisotrop ic magnetic turbulence, in which the magnetic fluctuating level and the cor relation lengths can be varied independently of each other, that the Kubo n umber also determines the level of chaos of the magnetic-held lines. We And weak chaos, dosed magnetic surfaces, and anomalous transport regimes for R much less than 1; widespread chaos, destroyed magnetic surfaces, and quasi linear scaling of the diffusion coefficient for R greater than or similar t o 0.3; and global stochasticity as well as the percolation scaling of the d iffusion coefficient for R much greater than 1. (C) 2000 Elsevier Science B .V. All rights reserved.