Helioseismic measurements of elemental abundances in the sun's interior

Abstract

The method of 'secondary' helioseismic inversion, in which the equations of state and the thermal balance are used in addition to the hydrostatic equations, have been applied to determine the helium abundance in the Sun's interior. By inverting the observed p-mode frequencies, direct evidence for gravitational settling of helium has been obtained. The helium abundance inferred from the BBSO data (Libbrechh et al., 1990)using the OPAL equation of state (Rogers & Iglesias, 1993)is 0.248 ± 0.006.