Sensitivity of the low degree oscillations to the change of solar abundances

Context. The most recent determination of the solar chemical composition by Asplund et al. (2005), using time-dependent, 3D hydrodynamical model of the solar atmosphere, exhibits a significant decrease on C, N, O abundances compared to their previous values. Solar models that use these new abundances are not consistent with helioseismological determinations of the sound speed profile, the surface helium abundance and the convection zone depth. Aims. We investigate the effect of changes of solar abundances on low degree p-mode and g-mode characteristics which are strong constraints of the solar core. We consider particularly the increase of neon abundance in the new solar mixture as suggested by Antia & Basu (2005) in order to reduce the discrepancy between models using new abundances and helioseismology. Methods. The very recent observational determinations of solar frequencies from GOLF instrument (Lazrek et al. 2007) are used to test solar models that are computed with different chemical compositions. We consider in particular the normalized small frequency spacings in low degree p-mode frequency range. Results. Low-degree small frequency spacings are very sensitive to the change on the heavy-element abundances, notably the neon abundance. We show that by considering all the seismic constraints, including the small frequency spacings, a rather large increase of neon abundance by about (0.5 ± 0.05)dex can be a good solution regarding the discrepancy between solar models that use new abundances and low degree helioseismology, subject to adjust slightly the solar age and the most profuse abundances. We also show that the change on solar abundances, notably neon abundance, affects considerably g-mode frequencies, with relative frequency differences between the old and the new models higher than 1.5%.