Nonlinear theory of a “shear-current” effect and mean-field magnetic dynamos

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94 Scopus citations

Abstract

The nonlinear theory of a “shear-current” effect in a nonrotating and nonhelical homogeneous turbulence with an imposed mean velocity shear is developed. The shear-current effect is associated with the [Formula presented] term in the mean electromotive force and causes the generation of the mean magnetic field even in a nonrotating and nonhelical homogeneous turbulence (where [Formula presented] is the mean vorticity and [Formula presented] is the mean electric current). It is found that there is no quenching of the nonlinear shear-current effect contrary to the quenching of the nonlinear [Formula presented] effect, the nonlinear turbulent magnetic diffusion, etc. During the nonlinear growth of the mean magnetic field, the shear-current effect only changes its sign at some value [Formula presented] of the mean magnetic field. The magnitude [Formula presented] determines the level of the saturated mean magnetic field which is less than the equipartition field. It is shown that the background magnetic fluctuations due to the small-scale dynamo enhance the shear-current effect and reduce the magnitude [Formula presented]. When the level of the background magnetic fluctuations is larger than [Formula presented] of the kinetic energy of the turbulence, the mean magnetic field can be generated due to the shear-current effect for an arbitrary exponent of the energy spectrum of the velocity fluctuations.

Original languageEnglish GB
Article number046310
Pages (from-to)15
Number of pages1
JournalPhysical Review E
Volume70
Issue number4
DOIs
StatePublished - 1 Jan 2004

ASJC Scopus subject areas

  • Statistical and Nonlinear Physics
  • Statistics and Probability
  • Condensed Matter Physics

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