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Title: Magnetic field line random walk in models and simulations of reduced magnetohydrodynamic turbulence

The random walk of magnetic field lines is examined numerically and analytically in the context of reduced magnetohydrodynamic (RMHD) turbulence, which provides a useful description of plasmas dominated by a strong mean field, such as in the solar corona. A recently developed non-perturbative theory of magnetic field line diffusion is compared with the diffusion coefficients obtained by accurate numerical tracing of magnetic field lines for both synthetic models and direct numerical simulations of RMHD. Statistical analysis of an ensemble of trajectories confirms the applicability of the theory, which very closely matches the numerical field line diffusion coefficient as a function of distance z along the mean magnetic field for a wide range of the Kubo number R. This theory employs Corrsin's independence hypothesis, sometimes thought to be valid only at low R. However, the results demonstrate that it works well up to R = 10, both for a synthetic RMHD model and an RMHD simulation. The numerical results from the RMHD simulation are compared with and without phase randomization, demonstrating a clear effect of coherent structures on the field line random walk for a very low Kubo number.
Authors:
;  [1] ;  [2] ;  [3] ;  [4]
  1. Department of Physics, Faculty of Science, Mahidol University, Bangkok 10400 (Thailand)
  2. Department of Mathematics, University of Waikato, Hamilton 3240 (New Zealand)
  3. Dipartimento di Fisica, Università della Calabria, I-87036 Cosenza (Italy)
  4. Bartol Research Institute and Department of Physics and Astronomy, University of Delaware, Newark, DE 19716 (United States)
Publication Date:
OSTI Identifier:
22348526
Resource Type:
Journal Article
Resource Relation:
Journal Name: Astrophysical Journal; Journal Volume: 779; 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; COMPARATIVE EVALUATIONS; COMPUTERIZED SIMULATION; DIFFUSION; MAGNETIC FIELDS; MAGNETOHYDRODYNAMICS; MEAN-FIELD THEORY; PLASMA; RANDOMNESS; SOLAR CORONA; TURBULENCE