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

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A1 Alkuperäisartikkeli tieteellisessä aikakauslehdessä
Date
2021-01-26
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Mcode
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Language
en
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Astronomy & Astrophysics
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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| openaire: EC/H2020/818665/EU//UniSDyn
Keywords
Astrophysics - Solar and Stellar Astrophysics
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Citation
Viviani , M & Käpylä , M J 2021 , ' Physically motivated heat conduction treatment in simulations of solar-like stars: effects on dynamo transitions ' , Astronomy & Astrophysics , vol. 645 , 141 . https://doi.org/10.1051/0004-6361/202038603