Laminar and Turbulent Dynamos in Chiral Magnetohydrodynamics. II. Simulations

Jennifer Schober, Igor Rogachevskii, Axel Brandenburg, Alexey Boyarsky, Jürg Fröhlich, Oleg Ruchayskiy, Nathan Kleeorin

Research output: Contribution to journalArticlepeer-review

55 Scopus citations

Abstract

Using direct numerical simulations (DNS), we study laminar and turbulent dynamos in chiral magnetohydrodynamics with an extended set of equations that accounts for an additional contribution to the electric current due to the chiral magnetic effect (CME). This quantum phenomenon originates from an asymmetry between left- and right-handed relativistic fermions in the presence of a magnetic field and gives rise to a chiral dynamo. We show that the magnetic field evolution proceeds in three stages: (1) a small-scale chiral dynamo instability, (2) production of chiral magnetically driven turbulence and excitation of a large-scale dynamo instability due to a new chiral effect (α μ effect), and (3) saturation of magnetic helicity and magnetic field growth controlled by a conservation law for the total chirality. The α μ effect becomes dominant at large fluid and magnetic Reynolds numbers and is not related to kinetic helicity. The growth rate of the large-scale magnetic field and its characteristic scale measured in the numerical simulations agree well with theoretical predictions based on mean-field theory. The previously discussed two-stage chiral magnetic scenario did not include stage (2), during which the characteristic scale of magnetic field variations can increase by many orders of magnitude. Based on the findings from numerical simulations, the relevance of the CME and the chiral effects revealed in the relativistic plasma of the early universe and of proto-neutron stars are discussed.

Original languageEnglish
Article number124
JournalAstrophysical Journal
Volume858
Issue number2
DOIs
StatePublished - 10 May 2018

Keywords

  • early universe
  • magnetic fields
  • magnetohydrodynamics (MHD)
  • relativistic processes
  • stars: Neutron
  • turbulence

ASJC Scopus subject areas

  • Astronomy and Astrophysics
  • Space and Planetary Science

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