Numerical studies of dynamo action in a turbulent shear flow - I

Abstract

We perform numerical experiments to study the shear dynamo problem where we look for the growth of large--scale magnetic field due to non--helical stirring at small scales in a background linear shear flow, in previously unexplored parameter regimes. We demonstrate the large--scale dynamo action in the limit when the fluid Reynolds number ($\mathrm{Re}$) is below unity whereas the magnetic Reynolds number ($\mathrm{Rm}$) is above unity; the exponential growth rate scales linearly with shear, which is consistent with earlier numerical works. The limit of low $\mathrm{Re}$ is particularly interesting, as seeing the dynamo action in this limit would provide enough motivation for further theoretical investigations, which may focus the attention to this analytically more tractable limit of $\mathrm{Re}<1$ as compared to more formidable limit of $\mathrm{Re}>1$. We also perform simulations in the regimes when, (i) both ($\mathrm{Re}$, $\mathrm{Rm}$) $<1$; (ii) $\mathrm{Re}>1$ & $\mathrm{Rm}<1$, and compute all components of the turbulent transport coefficients (${\alpha }_{ij}$ and ${\eta }_{ij}$) using the test--field method. A reasonably good agreement is seen between our results and the results of earlier analytical works (Sridhar & Singh 2010; Singh & Sridhar 2011) in the similar parameter regimes.

arXiv comment11 pages, 10 figures, Submitted to Astrophysical Journal

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Cited by in corpus (12)

• Dynamo theories
• Large-scale dynamo action due to $\alpha$ fluctuations in a linear shear flow
• The magnetic shear-current effect: generation of large-scale magnetic fields by the small-scale dynamo
• Coherent nonhelical shear dynamos driven by magnetic fluctuations at low Reynolds numbers
• On the existence of shear-current effects in magnetized burgulence
• On the shear-current effect: toward understanding why theories and simulations have mutually and separately conflicted
• Moffatt drift driven large scale dynamo due to $\alpha$ fluctuations with nonzero correlation times
• Mean field dynamo action in shearing flows. II: fluctuating kinetic helicity with zero mean
• Vorticity and magnetic dynamo from subsonic expansion waves
• Generation of large-scale magnetic fields due to fluctuating $\alpha$ in shearing systems
• Calculating turbulent transport tensors by averaging single plume dynamics and application to dynamos
• Mean-field dynamo due to spatiotemporal fluctuations of the turbulent kinetic energy