Kubo number and magnetic field line diffusion coefficient for anisotropic magnetic turbulence
The magnetic field line diffusion coefficients D{sub x} and D{sub y} are obtained by numerical simulations in the case that all the magnetic turbulence correlation lengths l{sub x}, l{sub y}, and l{sub z} are different. We find that the variety of numerical results can be organized in terms of the Kubo number, the definition of which is extended from R=({delta}B/B{sub 0})(l{sub {parallel}}/l{sub {perpendicular}}) to R=({delta}B/B{sub 0})(l{sub z}/l{sub x}), for l{sub x}{ge}l{sub y}. Here, l{sub {parallel}} (l{sub {perpendicular}}) is the correlation length along (perpendicular to) the average field B{sub 0}=B{sub 0}{cflx e}{sub z}. We have anomalous, non-Gaussian transport for R{approx_lt}0.1, in which case the mean square deviation scales nonlinearly with time. For R{approx_gt}1 we have several Gaussian regimes: an almost quasilinear regime for 0.1{approx_lt}R{approx_lt}1, an intermediate, transition regime for 1{approx_lt}R{approx_lt}10, and a percolative regime for R{approx_gt}10. An analytical form of the diffusion coefficient is proposed, D{sub i}=D({delta}Bl{sub z}/B{sub 0}l{sub x}){sup {mu}}(l{sub i}/l{sub x}){sup {nu}}l{sub x}{sup 2}/l{sub z}, which well describes the numerical simulation results in the quasilinear, intermediate, and percolative regimes.
- Sponsoring Organization:
- (US)
- OSTI ID:
- 40203410
- Journal Information:
- Physical Review E, Vol. 63, Issue 6; Other Information: DOI: 10.1103/PhysRevE.63.066405; Othernumber: PLEEE8000063000006066405000001; 182105PRE; PBD: Jun 2001; ISSN 1063-651X
- Publisher:
- The American Physical Society
- Country of Publication:
- United States
- Language:
- English
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