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Astron. Astrophys. 350, 310-317 (1999)


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Quadrupole moment of the Sun. Gravitational and rotational potentials

Stéphany Godier and Jean-Pierre Rozelot

Observatoire de la Côte d'Azur, Département CERGA UMR 6527 du CNRS, av. Copernic, F-06130 Grasse, France (godier,rozelot@obs-azur.fr)

Received 15 March 1999 / Accepted 9 July 1999

Abstract

The solar quadrupole moment J2 was computed taking into account an up-to-date solar model of mass and density, combined with a recent rotational model established from the helioseismic data, and including the effects of differential rotation with depth. To determine precisely the theoretical value of J2 of the Sun, we integrated the extended differential equation governing the fluids in hydrostatic equilibrium, and the Poisson equation for the gravitational potential. From this analysis, we deduced the profiles of J2, as a function of the radius and of the latitude, from the core to the surface. This study has given information on the distortion of the total potential which accounts for the gravitational and rotational potentials.

As a result of our analysis, we found J2 = 1.60.10-7 which respects the upper bound [FORMULA] derived from the best knowledge of the Moon's physical librations. Finally, we linked the profiles of J2 within the Sun to the solar interior structure mainly governed by the shear in the tachocline and just below the surface.

Key words: Sun: fundamental parameters – Sun: interior – Sun: rotation – Sun: transition region


© European Southern Observatory (ESO) 1999

Online publication: September 24, 1999

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