A CALIBRATION OF SOLAR ENVELOPE MODELS USING THE FREQUENCIES OF INTERMEDIATE-DEGREE SOLAR ACOUSTIC-OSCILLATIONS

The frequency dependence of the phase shift, which arises from the reflection of internal acoustic waves (p-modes) at the outer solar layers, can be determined from the accurately measured frequencies of intermediate-degree p-modes. This dependence is sensitive to the complicated structure of the outer solar layers, down to the depth of the second ionization zone of helium. It can be used to calibrate solar envelope models. We report the results of the direct tests of a variety of solar envelope models using the phase shift inferred from the solar oscillation frequencies.