New values of gravitational moments J2 and J4 deduced from helioseismology

TL;DR

This paper calculates the Sun's gravitational moments J2 and J4 using helioseismology data and stellar models, revealing that J4 is highly sensitive to near-surface rotational gradients.

Contribution

It introduces a method combining helioseismology and stellar modeling to refine gravitational moment estimates, emphasizing the impact of near-surface rotation gradients.

Findings

J4 is more sensitive to near-surface rotation gradients than J2.

The model incorporates recent helioseismic rotation profiles.

Results improve understanding of solar gravitational field variations.

Abstract

By applying the theory of slowly rotating stars to the Sun, the solar quadrupole and octopole moments J2 and J4 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 J2, J4 is investigated. The results show that the octopole moment J4 is much more sensitive than the quadrupole moment J2 to the subsurface radial gradient of rotation.