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Title: Complexity and diffusion of magnetic flux surfaces in anisotropic turbulence

The complexity of magnetic flux surfaces is investigated analytically and numerically in static homogeneous magnetic turbulence. Magnetic surfaces are computed to large distances in magnetic fields derived from a reduced magnetohydrodynamic model. The question addressed is whether one can define magnetic surfaces over large distances when turbulence is present. Using a flux surface spectral analysis, we show that magnetic surfaces become complex at small scales, experiencing an exponential thinning that is quantified here. The computation of a flux surface is of either exponential or nondeterministic polynomial complexity, which has the conceptual implication that global identification of magnetic flux surfaces and flux exchange, e.g., in magnetic reconnection, can be intractable in three dimensions. The coarse-grained large-scale magnetic flux experiences diffusive behavior. The link between the diffusion of the coarse-grained flux and field-line random walk is established explicitly through multiple scale analysis. The Kubo number controls both large and small scale limits. These results have consequences for interpreting processes such as magnetic reconnection and field-line diffusion in astrophysical plasmas.
Authors:
 [1] ; ; ;  [2] ;  [3] ;  [4]
  1. Dipartimento di Fisica, Università della Calabria, I-87036 Cosenza (Italy)
  2. Department of Physics and Astronomy, University of Delaware, Newark, DE (United States)
  3. Department of Physics, Faculty of Science, Mahidol University, Bangkok (Thailand)
  4. Department of Mathematics, University of Waikato, Hamilton (New Zealand)
Publication Date:
OSTI Identifier:
22357168
Resource Type:
Journal Article
Resource Relation:
Journal Name: Astrophysical Journal; Journal Volume: 785; Journal Issue: 1; Other Information: Country of input: International Atomic Energy Agency (IAEA)
Country of Publication:
United States
Language:
English
Subject:
79 ASTROPHYSICS, COSMOLOGY AND ASTRONOMY; ANISOTROPY; ASTROPHYSICS; DIFFUSION; KUBO FORMULA; MAGNETIC FIELDS; MAGNETIC FLUX; MAGNETIC RECONNECTION; MAGNETIC SURFACES; MAGNETOHYDRODYNAMICS; PLASMA; RANDOMNESS; SOLAR WIND; SUN; TURBULENCE