Cross-helicity effects and turbulent transport in magnetohydrodynamic flow

Abstract

In the presence of large-scale vortical motions and/or magnetic-field strains, the turbulent cross helicity (velocity--magnetic-field correlation in fluctuations) may contribute to the turbulent electromotive force and the Reynolds stress. These effects of cross helicity are considered to balance the primary effects of turbulence such as the turbulent magnetic diffusivity in magnetic-field evolution and the eddy viscosity in the momentum transport. The cross-helicity effects may suppress the enhanced transports due to turbulence. Physical interpretation of the effects is presented with special emphasis on the difference between the cross-helicity effect and the usual $\alpha$ or helicity effect in the dynamo action. The relative importance of the cross-helicity effect in dynamo action is validated with the aid of a direct numerical simulation (DNS) of the Kolmogorov flow with an imposed magnetic field. Several mechanisms that provide turbulence with the cross helicity are also discussed.

10 pages, 6 figures, Journal of Physics Conference Series: 13th European Turbulence Conference (ETC13)

References in corpus (3)

• Global-Scale Turbulent Convection and Magnetic Dynamo Action in the Solar Envelope
• Modeling the turbulent cross-helicity evolution: Production, dissipation, and transport rates
• The role of the Yoshizawa effect in the Archontis dynamo

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• Analysis of fast turbulent reconnection with self-consistent determination of turbulence timescale
• Cross-helicity effect on $\alpha$-type dynamo in non-equilibrium turbulence
• Effects of shell thickness on cross-helicity generation in convection-driven spherical dynamos
• Electromotive field in space and astrophysical plasmas