Issue |
A&A
Volume 485, Number 1, July I 2008
|
|
---|---|---|
Page(s) | 267 - 273 | |
Section | The Sun | |
DOI | https://doi.org/10.1051/0004-6361:200809351 | |
Published online | 16 April 2008 |
Turbulent magnetic pumping in a Babcock-Leighton solar dynamo model
Astronomy Department, Instituto de Astronomia, Geofísica e Ciências Atmosfêricas, Universidade de São Paulo, Rua do Matão 1226, São Paulo, Brazil e-mail: guerrero,dalpino@astro.iag.usp.br
Received:
3
January
2008
Accepted:
18
March
2000
Context. The turbulent pumping effect corresponds to the transport of magnetic flux due to the presence of density and turbulence gradients in convectively unstable layers. In the induction equation it appears as an advective term and for this reason it is expected to be important in the solar and stellar dynamo processes.
Aims. We explore the effects of turbulent pumping in a flux-dominated Babcock-Leighton solar dynamo model with a solar-like rotation law.
Methods. As a first step, only vertical pumping has been considered through the inclusion of a radial diamagnetic term in the induction equation. In the second step, a latitudinal pumping term was included and then, a near-surface shear was included.
Results. The
results reveal the importance of the pumping mechanism in
solving current limitations in mean field dynamo modeling, such
as the storage of the magnetic flux and the latitudinal
distribution of the sunspots. If a meridional
flow is assumed to be present only in the upper part of the
convective zone, it is the full turbulent pumping that
regulates both the
period of the solar cycle and the latitudinal distribution of
the sunspot activity. In models that consider shear near
the surface, a second shell of toroidal field is generated
above at all latitudes. If the full pumping is
also included, the polar toroidal fields are efficiently advected
inwards, and the toroidal magnetic activity survives only at
the observed latitudes near the equator.
With regard to the parity of the magnetic field, only
models that combine turbulent pumping with near-surface shear
always converge to the dipolar parity.
Conclusions. This result suggests that, under the Babcock-Leighton approach, the equartorward motion of the observed magnetic activity is governed by the latitudinal pumping of the toroidal magnetic field rather than by a large scale coherent meridional flow. Our results support the idea that the parity problem is related to the quadrupolar imprint of the meridional flow on the poloidal component of the magnetic field and the turbulent pumping positively contributes to wash out this imprint.
Key words: Sun: magnetic fields / Sun: activity
© ESO, 2008
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