Anomalous, quasilinear, and percolative regimes for magnetic-field-line transport in axially symmetric turbulence

We studied a magnetic turbulence axisymmetric around the unperturbed magnetic field for cases having different ratios l_/l_⊥. We find, in addition to the fact that a higher fluctuation level δB/B₀ makes the system more stochastic, that by increasing the ratio l_/l_⊥ at fixed δB/B₀, the stochasticity increases. It appears that the different transport regimes can be organized in terms of the Kubo number R=(δB/B₀)(l_/l_⊥). The simulation results are compared with the two analytical limits, that is the percolative limit and the quasilinear limit. When R1 weak chaos, closed magnetic surfaces, and anomalous transport regimes are found. When R≈1 the diffusion regime is Gaussian, and the quasilinear scaling of the diffusion coefficient D_⊥~(δB/B₀)² is recovered. Finally, for R1 the percolation scaling of the diffusion coefficient D_⊥~(δB/B₀)0.7 is obtained.