G. Zimbardo et al., Anomalous, quasilinear, and percolative regimes for magnetic-field-line transport in axially symmetric turbulence, PHYS REV E, 61(2), 2000, pp. 1940-1948
We studied a magnetic turbulence axisymmetric around the unperturbed magnet
ic field for cases having different ratios l(parallel to)/l(perpendicular t
o). We find, in addition to the fact that a higher fluctuation level delta
B/B-0 makes the system more stochastic, that by increasing the ratio l(para
llel to)/l(perpendicular to), at fixed delta B/B-0, the stochasticity incre
ases. It appears that the different transport regimes can be organized in t
erms of the Kubo number R = (delta B/B-0)(l(parallel to)/l(perpendicular to
)). The simulation results are compared with the two analytical limits, tha
t is the percolative limit and the quasilinear limit. When R much less than
1 weak chaos, closed magnetic surfaces, and anomalous transport regimes ar
e found. When R approximate to 1 the diffusion regime is Gaussian, and the
quasilinear scaling of the diffusion coefficient D(perpendicular to)similar
to(delta B/B-0)(2) is recovered. Finally, for R much greater than 1 the pe
rcolation sealing of the diffusion coefficient D(perpendicular to)similar t
o(delta B/B-0)(0.7) is obtained.