New values of gravitational moments J2and J4deduced from helioseismology

Abstract

By applying the theory of slowly rotating stars to the Sun, the solar quadrupole and octopole moments J 2 and J 4 were computed using a solar model obtained from CESAM stellar evolution code (Morel, 1997) combined with a recent model of solar differential rotation deduced from helioseismology (Corbard et al., 2002). This model takes into account a near-surface radial gradient of rotation which was inferred and quantified from MDI f-mode observations by Corbard and Thompson (2002). The effect of this observational near-surface gradient on the theoretical values of the surface parameters J 2, J 4 is investigated. The results show that the octopole moment J 4 is much more sensitive than the quadrupole moment J 2 to the subsurface radial gradient of rotation.