Suppression of small-scale dynamo in time-irreversible turbulence

ABSTRACT The conventional theory of small-scale magnetic field generation in a turbulent flow considers time-reversible random flows. However, real turbulent flows are known to be time irreversible: the presence of energy cascade is an intrinsic property of turbulence. We generalize the ‘standard’ m...

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Bibliographic Details
Published in:Monthly notices of the Royal Astronomical Society 2024-01, Vol.527 (1), p.1055-1061
Main Authors: Kopyev, A V, Il’yn, A S, Sirota, V A, Zybin, K P
Format: Article
Language:English
Subjects:
Fluid dynamics
Fluid flow
Magnetic properties
Reynolds number
Turbulence
Turbulent flow
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Summary:ABSTRACT The conventional theory of small-scale magnetic field generation in a turbulent flow considers time-reversible random flows. However, real turbulent flows are known to be time irreversible: the presence of energy cascade is an intrinsic property of turbulence. We generalize the ‘standard’ model to account for the irreversibility. We show that even small time asymmetry leads to significant suppression of the dynamo effect at low magnetic Prandtl numbers, increases the generation threshold, and may even make generation impossible for any magnetic Reynolds number. We calculate the magnetic energy growth rate as a function of the parameters of the flow.
ISSN:0035-8711
1365-2966
DOI:10.1093/mnras/stad3191