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Magnetic dynamo action in two-dimensional turbulent magneto-hydrodynamics

Published online by Cambridge University Press:  13 March 2009

David Fyfe
Affiliation:
Department of Physics and Astronomy, University of Iowa, Iowa City, Iowa 52242
Glenn Joyce
Affiliation:
Department of Physics and Astronomy, University of Iowa, Iowa City, Iowa 52242
David Montgomery
Affiliation:
Advanced Study Program, National Center for Atmospheric Research, Boulder, Colorado 80303

Abstract

Two-dimensional magnetohydrodynamic turbulence is explored by means of numerical simulation. Previous analytical theory, based on non-dissipative constants of the motion in a truncated Fourier representation, is verified by following the evolution of highly non-equilibrium initial conditions numerically. Dynamo action (conversion of a significant fraction of turbulent kinetic energy into long-wavelength magnetic field energy) is observed. It is conjectured that in the presence of dissipation and external forcing; a dual cascade will be observed for zero-helicity situations. Energy will cascade to higher wavenumbers simultaneously with a cascade of mean square vector potential to lower wavenumbers, leading to an omni-directional magnetic energy spectrum which varies as k-⅓ at lower wavenumbers, simultaneously with a build-up of magnetic excitation at the lowest wavenumber of the system. Equipartition of kinetic and magnetic energies is expected at the highest wavenumbers in the system.

Type
Research Article
Copyright
Copyright © Cambridge University Press 1977

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