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(Reference retrieved automatically from Web of Science through information on FAPESP grant and its corresponding number as mentioned in the publication by the authors.)

ON THE ROLE OF TACHOCLINES IN SOLAR AND STELLAR DYNAMOS

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Author(s):
Guerrero, G. [1] ; Smolarkiewicz, P. K. [2] ; de Gouveia Dal Pino, E. M. [3] ; Kosovichev, A. G. [4] ; Mansour, N. N. [5]
Total Authors: 5
Affiliation:
[1] Univ Fed Minas Gerais, Dept Phys, Ave Antonio Carlos 6627, BR-31270901 Belo Horizonte, MG - Brazil
[2] European Ctr Medium Range Weather Forecasts, Shinfield Pk, Reading RG2 9AX, Berks - England
[3] Univ Sao Paulo, IAG, Dept Astron, Rua Mato 1226, BR-05508090 Sao Paulo, SP - Brazil
[4] New Jersey Inst Technol, Newark, NJ 07103 - USA
[5] NASA, Ames Res Ctr, Mountain View, CA 94040 - USA
Total Affiliations: 5
Document type: Journal article
Source: ASTROPHYSICAL JOURNAL; v. 819, n. 2 MAR 10 2016.
Web of Science Citations: 22
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 similar to 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 similar to 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. (AU)

FAPESP's process: 13/11679-4 - Cosmic magnetic fields: from the generation mechanism to the solar activity and the Sun-Earth connection
Grantee:Gustavo Andres Guerrero Eraso
Support type: Scholarships in Brazil - Post-Doctorate
FAPESP's process: 09/54006-4 - A computer cluster for the Astronomy Department of the University of São Paulo Institute of Astronomy, Geophysics and Atmospheric Sciences and for the Cruzeiro do Sul University Astrophysics Center
Grantee:Elisabete Maria de Gouveia Dal Pino
Support type: Multi-user Equipment Program
FAPESP's process: 13/10559-5 - Investigation of high energy and plasma astrophysics phenomena: theory, numerical simulations, observations, and instrument development for the Cherenkov Telescope Array (CTA)
Grantee:Elisabete Maria de Gouveia Dal Pino
Support type: Research Projects - Thematic Grants