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Are tachoclines important for solar and stellar dynamos? What can we learn from global simulations

Published online by Cambridge University Press:  12 September 2017

G. Guerrero ,
P. K. Smolarkiewicz ,
E. M. de Gouveia Dal Pino ,
A. G. Kosovichev ,
B. Zaire  and
N. N. Mansour
G. Guerrero
Affiliation:
Physics Department, Universidade Federal de Minas Gerais, Av. Presidente Antonio Carlos 6627, Belo Horizonte, MG, 31270-901, Brazil, email: [email protected]
P. K. Smolarkiewicz
Affiliation:
European Centre for Medium-Range Weather Forecasts, Reading RG2 9AX, UK
E. M. de Gouveia Dal Pino
Affiliation:
Astronomy Department, IAG-USP, Rua do Matão, 1226, SP, 05508-090, Brazil
A. G. Kosovichev
Affiliation:
New Jersey Institute of Technology, Newark, NJ 07103, USA
B. Zaire
Affiliation:
Physics Department, Universidade Federal de Minas Gerais, Av. Presidente Antonio Carlos 6627, Belo Horizonte, MG, 31270-901, Brazil, email: [email protected]
N. N. Mansour
Affiliation:
NASA, Ames Research Center, Moffett Field, Mountain View, CA 94040, USA
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Abstract

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The role of tachoclines, the thin shear layers that separate solid body from differential rotation in the interior of late-type stars, in stellar dynamos is still controversial. In this work we discuss their relevance in view of recent results from global dynamo simulations performed with the EULAG-MHD code. The models have solar-like stratification and different rotation rates (i.e., different Rossby number). Three arguments supporting the key role of tachoclines are presented: the solar dynamo cycle period, the origin of torsional oscillations and the scaling law of stellar magnetic fields as function of the Rossby number. This scaling shows a regime where the field strength increases with the rotation and a saturated regime for fast rotating stars. These properties are better reproduced by models that consider the convection zone and a fraction of the radiative core, naturally developing a tachocline, than by those that consider only the convection zone.

Keywords

StarsrotationStars: magnetismStars: dynamo
Type
Contributed Papers
Information
Proceedings of the International Astronomical Union , Volume 12 , Symposium S328: Living Around Active Stars , October 2016 , pp. 61 - 68
Copyright
Copyright © International Astronomical Union 2017 

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