Understanding the solar tachocline: testing the magnetic confinement
scenario with numerical simulations.
Antoine Strugarek
CEA Saclay, France
Among the many fascinating aspects of the solar dynamics, the structure
of the tachocline (thin region located at 0.7 solar radius in the interior
of the Sun) has been puzzling the solar physicists for many years. In
particular, its extreme thinness (less than 5% of the solar radius) has
not been satisfactorily explained yet. Some theoretical models have been
proposed to explain its structure, among which one postulated the
existence of a (fossil) magnetic field, buried in the radiative interior
of the Sun, that would confine the tachocline to a thin layer. We present
pioneer 3D MHD global solar simulations coupling the turbulent convective
zone and the radiative zone that have been carried out to test this
scenario. Essential features of the Sun, such as differential rotation,
meridional circulation and internal waves excitation are recovered. We
find that an initially confined axisymmetric dipolar fossil field does not
confine the tachocline and couples the convection zone to the solar
interior. The three- dimensional convective motions are shown to play an
essential role in the transport of magnetic field and the failure of the
confinement scenario. Because of its axisymmetry, the dipolar field is
moreover able to transport the mean angular momentum radially,
accelerating the loss of confinement of the tachocline. Other primordial
magnetic field configurations are also considered. We find a similar
evolution of the solar interior in the case of an inclined dipole (with
respect to the rotation axis of the star). The special case of a
perpendicular dipolar magnetic field results in a significantly different
evolution compared the aligned dipolar case. Nevertheless, the magnetic
confinement scenario for the tachocline fails in the three cases, in the
parameter regime we have explored.
Date: | Jeudi, le 13 décembre 2012 |
Heure: | 11:30 |
Lieu: | Université de Montréal |
| Pavillon Roger-Gaudry, local D-460 |
Contact: | Paul Charbonneau |
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