On the Sensitivity of HighDegree pMode Frequencies to the Solar Convection Zone Helium Abundance
Abstract
Nonadiabatic frequencies for modes of degree l = 2001000 for the MHD equation of state model described in Guzik and Cox (1991) with a convection zone Y = 0.27 are compared with a model with Y = 0.24, corresponding to the decrease expected due to diffusion. The frequencies of the l = 300600 modes, which sample best the helium ionization region, show the greatest sensitivity to this helium abundance change. The frequency sensitivity to helium abundances is not affected by changes in the mixinglength/pressure scale height ratio or the inclusion of the turbulent pressure, although these effects can alter considerably the upper convection zone structure and the calculated frequencies. The observed minus calculated frequency differences for these highdegree loworder modes are discussed. The O  C differences for the accurately observed modes favor a reduction in the convection zone helium mass fraction of about 0.3, consistent with that expected due to diffusion.
 Publication:

The Astrophysical Journal
 Pub Date:
 February 1992
 DOI:
 10.1086/171054
 Bibcode:
 1992ApJ...386..729G
 Keywords:

 Abundance;
 Convection;
 Helium;
 Solar Interior;
 Solar Oscillations;
 Equations Of State;
 Frequency Distribution;
 Magnetohydrodynamics;
 Opacity;
 Stellar Models;
 Solar Physics;
 SUN: ABUNDANCES;
 SUN: INTERIOR;
 SUN: OSCILLATIONS