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  Physically motivated heat conduction treatment in simulations of solar-like stars: effects on dynamo transitions

Viviani, M., & Käpylä, M. J. (2021). Physically motivated heat conduction treatment in simulations of solar-like stars: effects on dynamo transitions. Astronomy and Astrophysics, 645: A141. doi:10.1051/0004-6361/202038603.

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 Creators:
Viviani, Mariangela1, Author              
Käpylä, Maarit J.2, 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, ou_2265638              

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Free keywords: magnetohydrodynamics (MHD) / convection / turbulence / Sun: activity / dynamo
 Abstract: Context. Results from global magnetoconvection simulations of solar-like stars are at odds with observations in many respects: simulations show a surplus of energy in the kinetic power spectrum at large scales; anti-solar differential rotation profiles with accelerated poles, and a slow equator for the solar rotation rate; and a transition from axi- to nonaxisymmetric dynamos at a much lower rotation rate than what is observed. Even though the simulations reproduce the observed active longitudes in fast rotators, their motion in the rotational frame (the so-called azimuthal dynamo wave, ADW) is retrograde, in contrast to the prevalent prograde motion in observations. Aims. We study the effect of a more realistic treatment of heat conductivity in alleviating the discrepancies between observations and simulations. Methods. We use physically motivated heat conduction by applying Kramers opacity law to a semi-global spherical setup that describes the convective envelopes of solar-like stars, instead of a prescribed heat conduction profile from mixing-length arguments. Results. We find that some aspects of the results now better correspond to observations: the axi- to nonaxisymmetric transition point is shifted towards higher rotation rates. We also find a change in the propagation direction of ADWs that means that prograde waves are also now found. However, the transition from an anti-solar to solar-like rotation profile is also shifted towards higher rotation rates, leaving the models in an even more unrealistic regime. Conclusions. Although Kramers-based heat conduction does not help in reproducing the solar rotation profile, it does help in the faster rotation regime, where the dynamo solutions now better match the observations.

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Language(s): eng - English
 Dates: 2021
 Publication Status: Published online
 Pages: -
 Publishing info: -
 Table of Contents: -
 Rev. Type: Peer
 Degree: -

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Title: Astronomy and Astrophysics
  Other : Astron. Astrophys.
Source Genre: Journal
 Creator(s):
Affiliations:
Publ. Info: Les Ulis Cedex A France : EDP Sciences
Pages: - Volume / Issue: 645 Sequence Number: A141 Start / End Page: - Identifier: ISSN: 1432-0746
ISSN: 0004-6361
CoNE: https://pure.mpg.de/cone/journals/resource/954922828219_1