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Type:	Artigo de Periódico
Title:	On the role of tachoclines in solar and stellar dynamos
Authors:	Gustavo Andres Guerrero Eraso Piotr Krzysztof Smolarkiewicz Elisabete Maria de Gouveia Dal Pino Alexander. G. Kosovichev Nagi Nicolas Mansour
Abstract:	Rotational shear layers at the boundary between radiative and convective zones, tachoclines, play a key role in the process of magnetic field generation in solar-like stars. We present two sets of global simulations of rotating turbulent convection and dynamo. The first set considers a stellar convective envelope only; the second one, aiming at the formation of a tachocline, also considers the upper part of the radiative zone. Our results indicate that the resulting properties of the mean flows and dynamo, such as the growth rate, saturation energy, and mode, depend on the Rossby number (Ro). For the first set of models either oscillatory (with ∼2 yr period) or steady dynamo solutions are obtained. The models in the second set naturally develop a tachocline, which in turn leads to the generation of a strong mean magnetic field. Since the field is also deposited in the stable deeper layer, its evolutionary timescale is much longer than in the models without a tachocline. Surprisingly, the magnetic field in the upper turbulent convection zone evolves on the same timescale as the deep field. These models result in either an oscillatory dynamo with a ∼30 yr period or a steady dynamo depending on Ro. In terms of the mean-field dynamo coefficients computed using the first-order smoothing approximation, the field evolution in the oscillatory models without a tachocline seems to be consistent with dynamo waves propagating according to the Parker–Yoshimura sign rule. In the models with tachoclines the dynamics is more complex and involves other transport mechanisms as well as tachocline instabilities.
Subject:	Estrelas Sol Solar magnetic fields Solar rotation
language:	eng
metadata.dc.publisher.country:	Brasil
Publisher:	Universidade Federal de Minas Gerais
Publisher Initials:	UFMG
metadata.dc.publisher.department:	ICX - DEPARTAMENTO DE FÍSICA
Rights:	Acesso Aberto
metadata.dc.identifier.doi:	https://doi.org/10.3847/0004-637X/819/2/104
URI:	http://hdl.handle.net/1843/60312
Issue Date:	2016
metadata.dc.url.externa:	https://iopscience.iop.org/article/10.3847/0004-637X/819/2/104
metadata.dc.relation.ispartof:	The Astrophysical Journal
Appears in Collections:	Artigo de Periódico

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