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  Turbulent transport coefficients in spherical wedge dynamo simulations of solar-like stars

Warnecke, J., Rheinhardt, M., Tuomisto, S., Käpylä, P. J., Käpylä, M. J., & Brandenburg, A. (2018). Turbulent transport coefficients in spherical wedge dynamo simulations of solar-like stars. Astronomy and Astrophysics, 609: A51. doi:10.1051/0004-6361/201628136.

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Item Permalink: http://hdl.handle.net/21.11116/0000-0000-2676-1 Version Permalink: http://hdl.handle.net/21.11116/0000-0000-2677-0
Genre: Journal Article

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 Creators:
Warnecke, Jörn1, 2, Author              
Rheinhardt, M., Author
Tuomisto, S., Author
Käpylä, P. J., Author
Käpylä, Maarit J.1, 2, Author              
Brandenburg, A., Author
Affiliations:
1Department Sun and Heliosphere, Max Planck Institute for Solar System Research, Max Planck Society, ou_1832289              
2Max Planck Research Group in Solar and Stellar Magnetic Activity, Max Planck Institute for Solar System Research, Max Planck Society, Justus-von-Liebig-Weg 3, 37077 Göttingen, DE, ou_2265638              

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 MPIS_GROUPS: Research Group Solar Stellar Mag Activity
 Abstract: Aims. We investigate dynamo action in global compressible solar-like convective dynamos in the framework of mean-field theory. Methods. We simulate a solar-type star in a wedge-shaped spherical shell, where the interplay between convection and rotation self-consistently drives a large-scale dynamo. To analyze the dynamo mechanism we apply the test-field method for azimuthally (φ) averaged fields to determine the 27 turbulent transport coefficients of the electromotive force, of which six are related to the α tensor. This method has previously been used either in simulations in Cartesian coordinates or in the geodynamo context and is applied here for the first time to fully compressible simulations of solar-like dynamos. Results. We find that the φφ-component of the α tensor does not follow the profile expected from that of kinetic helicity. The turbulent pumping velocities significantly alter the effective mean flows acting on the magnetic field and therefore challenge the flux transport dynamo concept. All coefficients are significantly affected by dynamically important magnetic fields. Quenching as well as enhancement are being observed. This leads to a modulation of the coefficients with the activity cycle. The temporal variations are found to be comparable to the time-averaged values and seem to be responsible for a nonlinear feedback on the magnetic field generation. Furthermore, we quantify the validity of the Parker-Yoshimura rule for the equatorward propagation of the mean magnetic field in the present case.

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Language(s): eng - English
 Dates: 2018-01-122018
 Publication Status: Published online
 Pages: -
 Publishing info: -
 Table of Contents: -
 Rev. Type: Peer
 Identifiers: DOI: 10.1051/0004-6361/201628136
 Degree: -

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Title: Astronomy and Astrophysics
  Other : Astron. Astrophys.
Source Genre: Journal
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Publ. Info: Berlin : Springer-Verlag
Pages: - Volume / Issue: 609 Sequence Number: A51 Start / End Page: - Identifier: ISSN: 0004-6361
CoNE: https://pure.mpg.de/cone/journals/resource/954922828219_1