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Astron. Astrophys. 363, L13-L16 (2000)


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Letter to the Editor

Spatiotemporal fragmentation as a mechanism for different dynamical modes of behaviour in the solar convection zone

E. Covas;1  * , R. Tavakol;1  ** and D. Moss;2  ***

1 Queen Mary and Westfield College, Astronomy Unit, School of Mathematical Sciences, Mile End Road, London E1 4NS, UK
2 The University, Department of Mathematics, Manchester M13 9PL, UK

Received 14 August 2000 / Accepted 17 October 2000

Abstract

Recent analyses of the helioseismic observations indicate that the previously observed surface torsional oscillations with periods of about 11 years extend significantly downwards into the solar convective zone. Furthermore, there are indications that the dynamical regimes at the base of the convection zone are different from those observed at the top, having either significantly shorter periods or non-periodic behaviour.

We propose that this behaviour can be explained by the occurrence of spatiotemporal fragmentation , a crucial feature of which is that such behaviour can be explained solely through nonlinear spatiotemporal dynamics, without requiring separate mechanisms with different time scales at different depths.

We find evidence for this mechanism in the context of a two dimensional axisymmetric mean field dynamo model operating in a spherical shell, with a semi-open outer boundary condition, in which the only nonlinearity is the action of the azimuthal component of the Lorentz force of the dynamo generated magnetic field on the solar angular velocity.

Key words: Sun: magnetic fields – Sun: oscillations – Sun: activity

* eoc@maths.qmw.ac.uk
** reza@maths.qmw.ac.uk
*** moss@ma.man.ac.uk

Send offprint requests to: E. Covas

© European Southern Observatory (ESO) 2000

Online publication: December 5, 2000

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