Inferences of Element Abundances from Helioseismic Data

. The abundance of helium in the Sun's interior is estimated by the method of `model-oriented' helioseismic inversion of solar oscillation frequencies. In this method, the equations of state and thermal balance are used in addition to the hydrostatic equation. By inverting the observed p-mode frequencies, direct evidence for gravitational settling of helium has been obtained. However, the helium settling cannot account for the anomalously low helium abundance of the solar corona and wind. The ratio of the helium to hydrogen densities in the convection zone inferred from the helioseismic data [1,2] using the most recent equation of state [3] is 8:5% \Sigma 0:2% suggesting that the separation of helium and hydrogen predominantly occurs in the solar atmosphere and corona. INTRODUCTION Helioseismic inversion of solar oscillation frequencies is a unique tool for inferring the physical properties of the Sun's interior. The frequencies of several thousand acoustic modes of the oscillations i..