Quenching and anisotropy of hydromagnetic turbulent transport
Hydromagnetic turbulence affects the evolution of largescale magnetic fields through meanfield effects like turbulent diffusion and the α effect. For stronger fields, these effects are usually suppressed or quenched, and additional anisotropies are introduced. Using different variants of the testfield method, we determine the quenching of the turbulent transport coefficients for the forced Roberts flow, isotropically forced nonhelical turbulence, and rotating thermal convection. We see significant quenching only when the mean magnetic field is larger than the equipartition value of the turbulence. Expressing the magnetic field in terms of the equipartition value of the quenched flows, we obtain for the quenching exponents of the turbulent magnetic diffusivity about 1.3, 1.1, and 1.3 for Roberts flow, forced turbulence, and convection, respectively. However, when the magnetic field is expressed in terms of the equipartition value of the unquenched flows, these quenching exponents become about 4, 1.5, and 2.3, respectively. For the α effect, the exponent is about 1.3 for the Roberts flow and 2 for convection in the first case, but 4 and 3, respectively, in the second. In convection, the quenching of turbulent pumping follows the same power law as turbulent diffusion, while for the coefficient describing the Ω×J effect nearlymore »
 Authors:

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 Nordita, KTH Royal Institute of Technology and Stockholm University, Roslagstullsbacken 23, SE10691 Stockholm (Sweden)
 Department of Physics, Gustaf Hällströmin katu 2a, P.O. Box 64, FI00014 University of Helsinki (Finland)
 ReSoLVE Centre of Excellence, Department of Information and Computer Science, Aalto University, P.O. Box 15400, FI00076 Aalto (Finland)
 Publication Date:
 OSTI Identifier:
 22370326
 Resource Type:
 Journal Article
 Resource Relation:
 Journal Name: Astrophysical Journal; Journal Volume: 795; 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; AXIAL SYMMETRY; DIFFUSION; HYDROMAGNETIC WAVES; MAGNETIC FIELDS; MAGNETIC REYNOLDS NUMBER; MAGNETOHYDRODYNAMICS; MEANFIELD THEORY; QUENCHING; STAR EVOLUTION; TURBULENCE