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  Mean field dynamo action in shear flows. I: fixed kinetic helicity

Jingade, N., & Singh, N. K. (2020). Mean field dynamo action in shear flows. I: fixed kinetic helicity. Monthly Notices of the Royal Astronomical Society, 495(4), 4557-4569. doi:10.1093/mnras/staa1204.

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Item Permalink: http://hdl.handle.net/21.11116/0000-0006-C85D-1 Version Permalink: http://hdl.handle.net/21.11116/0000-0006-C85E-0
Genre: Journal Article

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 Creators:
Jingade, Naveen, Author
Singh, Nishant K.1, Author              
Affiliations:
1Max Planck Research Group in Solar and Stellar Magnetic Activity, Max Planck Institute for Solar System Research, Max Planck Society, ou_2265638              

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 Abstract: We study mean field dynamo action in a background linear shear flow by employing pulsed renewing flows with fixed kinetic helicity and non-zero correlation time (tau). We use plane shearing waves in terms of time-dependent exact solutions to the Navier-Stokes equation as derived by Singh & Sridhar (2017). This allows us to self-consistently include the anisotropic effects of shear on the stochastic flow. We determine the average response tensor governing the evolution of mean magnetic field, and study the properties of its eigenvalues that yield the growth rate (gamma) and the cycle period (P-cyc) of the mean magnetic field. Both, gamma and the wavenumber corresponding to the fastest growing axisymmetric mode vary non-monotonically with shear rate S when v is comparable to the eddy turnover time T, in which case, we also find quenching of dynamo when shear becomes too strong. When tau/T similar to O(1), the cycle period (P-cyc) of growing dynamo wave scales with shear as P-cyc proportional to vertical bar S vertical bar(-1) at small shear, and it becomes nearly independent of shear as shear becomes too strong. This asymptotic behaviour at weak and strong shear has implications for magnetic activity cycles of stars in recent observations. Our study thus essentially generalizes the standard alpha Omega (or alpha(2)Omega) dynamo as also the a effect is affected by shear and the modelled random flow has a finite memory.

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Language(s): eng - English
 Dates: 2020
 Publication Status: Published in print
 Pages: -
 Publishing info: -
 Table of Contents: -
 Rev. Type: Peer
 Identifiers: DOI: 10.1093/mnras/staa1204
 Degree: -

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Title: Monthly Notices of the Royal Astronomical Society
  Other : Mon. Not. R. Astron. Soc.
Source Genre: Journal
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Publ. Info: Oxford : Oxford University Press
Pages: - Volume / Issue: 495 (4) Sequence Number: - Start / End Page: 4557 - 4569 Identifier: ISSN: 1365-8711
CoNE: https://pure.mpg.de/cone/journals/resource/1000000000024150