THE ROTATION OF THE SUNS CORE

The rotation of the Sun's core, below 0.3 .,, is inferred from two ind ependent new results. The first is based on the recent oblateness meas urements carried out by the Solar Disk Sextant (SDS) instrument outsid e the Earth's atmosphere, and the second on the very accurate measurem ents of rotational splittings of the lowest degree acoustic modes, car ried out in the framework of the helioseismic network IRIS. By using t he theory of slowly rotating stars applied to a solar standard model, we deduce a set of rotational laws for the innermost layers, which are consistent with both the measured oblateness value and the results of the inversion of helioseismic data. The SDS and IRIS results indicate that the Sun's central regions rotate at a rate in between 1.5 and 2 times the surface equatorial angular velocity. As a result of our anal ysis, we deduce a quadrupole moment J(2)=2.22 x 10(-7), which implies an advance of Mercury's perihelion of 42.98 arc-s/c, in agreement with the theory of General Relativity and the measurements of Mercury's or bit by means of planetary radar ranging. However, very recent results obtained by the helioseismic network BISON indicate that core rotation is even slower than the polar surface rotation and therefore imply a completely different scenario than that proposed here. If we assume th e intermediate solution of rigid body rotation, an alternate source of the oblateness may be attributed to a magnetic field of the order of 10(5) Gauss in the interior of the Sun.