The Depth of the Solar Convection Zone

The transition of the temperature gradient between being subadiabatic and adiaba tic at the base of the solar convection zone gives rise to a clear signature in the sound speed. Helioseismic measurements of the sound speed therefore permit a determination of the location of the base of the convection zone. We have tested two techniques by applying them to artificial data, obtained by adding simulated noise to frequencies computed from two different solar models. The determinations appear to be relatively insensitive to uncertainties of the physics of the solar interior, although, if present, a large-scale megagauss magnetic field or some other phenomenon not normally incorporated into theoretical models at the base of the convection zone might have a significant effect on the results. On the assumption that this is not the case, we conclude, from an analysis of observed frequencies of solar oscillation, that the depth of the solar convection zone is (0.287 ± 0.003) solar radii Subject headings : Sun: abundances — Sun: interior — Sun: oscillations