Magnetic fluctuations and formation of large-scale inhomogeneous magnetic structures in a turbulent convection

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71 Scopus citations

Abstract

Magnetic fluctuations generated by a tangling of the mean magnetic field by velocity fluctuations are studied in a developed turbulent convection with large magnetic Reynolds numbers. We show that the energy of magnetic fluctuations depends on the magnetic Reynolds number only when the mean magnetic field is smaller than Beq/4 Rm1/4, where Beq is the equipartition mean magnetic field determined by the turbulent kinetic energy and Rm is the magnetic Reynolds number. Generation of magnetic fluctuations in a turbulent convection with a nonzero mean magnetic field results in a decrease of the total turbulent pressure and may cause the formation of large-scale inhomogeneous magnetic structures even in an originally uniform mean magnetic field. This effect is caused by a negative contribution of the turbulent convection to the effective mean Lorentz force. The inhomogeneous large-scale magnetic fields are formed due to excitation of the large-scale instability. The energy for this instability is supplied by small-scale turbulent convection. The discussed effects might be useful for understanding the origin of solar nonuniform magnetic fields: e.g., sunspots.

Original languageEnglish
Article number056307
JournalPhysical Review E
Volume76
Issue number5
DOIs
StatePublished - 12 Nov 2007

ASJC Scopus subject areas

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

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