Cross-helicity effect on α-type dynamo in non-equilibrium turbulence

Turbulence is typically not in equilibrium, i.e. mean quantities such as the mean energy and helicity are typically time-dependent. The effect of non-stationarity on the turbulent hydromagnetic dynamo process is studied here with the use of the two-scale direct-interaction approximation, which allow...

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Bibliographic Details
Published in:Journal of plasma physics 2023-08, Vol.89 (4), Article 905890412
Main Authors: Mizerski, Krzysztof A., Yokoi, Nobumitsu, Brandenburg, Axel
Format: Article
Language:English
Subjects:
astrophysical plasmas
Electric potential
Electromotive forces
Equilibrium
Helicity
Investigations
Magnetic fields
Magnetohydrodynamic turbulence
plasma dynamics
plasma nonlinear phenomena
Plasma physics
Response functions
Symmetry
Velocity
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Summary:Turbulence is typically not in equilibrium, i.e. mean quantities such as the mean energy and helicity are typically time-dependent. The effect of non-stationarity on the turbulent hydromagnetic dynamo process is studied here with the use of the two-scale direct-interaction approximation, which allows one to explicitly relate the mean turbulent Reynolds and Maxwell stresses and the mean electromotive force to the spectral characteristics of turbulence, such as the mean energy, as well as kinetic and cross-helicity. It is demonstrated that the non-equilibrium effects can enhance the dynamo process when the magnetohydrodynamic turbulence is both helical and cross-helical. This effect is based on the turbulent infinitesimal-impulse cross-response functions, which do not affect turbulent flows in equilibrium. The evolution and sources of the cross-helicity in magnetohydrodynamic turbulence are also discussed.
ISSN:0022-3778
1469-7807
1469-7807
DOI:10.1017/S0022377823000545