P. Pommois et al., Kubo number and magnetic field line diffusion coefficient for anisotropic magnetic turbulence - art. no. 066405, PHYS REV E, 6306(6), 2001, pp. 6405
The magnetic line diffusion coefficients D-x and D-y are obtained by numeri
cal simulations in the case that all the magnetic turbulence correlation le
ngths l(x), l(y), and l(z) are different. We find that the variety of numer
ical results can be organized in terms of the Kubo number, the definition o
f which is extended from R = (deltaB/B-o) (l(parallel to)/l(perpendicular t
o)) to R = (deltaB/B-o)(l(z)/l(x)), for l(x)greater than or equal tol(y). H
ere, l(parallel to) (l(perpendicular to)) is the correlation length along (
perpendicular to) the average field B-o = B-o(e) over cap (z). We have anom
alous, non-Gaussian transport for R less than or similar to0.1, in which ca
se the mean square deviation scales nonlinearly with time. For R greater th
an or similar to 1 we have several Gaussian regimes: an almost quasilinear
regime for 0.1 less than or similar toR less than or similar to1. an interm
ediate, transition regime for 1 less than or similar toR less than or simil
ar to 10, and a percolative regime for R greater than or similar to 10. An
analytical form of the diffusion coefficient is proposed. D-i = D(delta Bl(
z)lB(o)l(x))(mu)(l(i)/l(x))(v)l(x)(2)/l(z), which well describes the numeri
cal simulation results in the quasilinear, intermediate, and percolative re
gimes.