Probing the interior of the sun and stars wtth acoustic modes of oscillation

For reasons which are, at present, poorly understood, the sun and presumably stars like the sun undergo continuous oscillations. The most prominant of these have been identified as normal modes which are gravity-modified acoustic resonances involving the whole sun. The spatial structure of the modes is described as the product of spherical harmonics Ylm (θ,φ) and a radial eigenfunction. The value of l determines the depth of mode penetration for each value of n. The identification of the modes with l and n permits a comparison of the observed frequencies with theoretical ones and tests the adequacy of our solar models. The frequency degeneracy in m is broken by rotation, and the measurement of the fine structure of the frequencies permits a determination of the depth dependence of the solar rotation rate. Present results indicate that the sun does not deviate substantially from a condition of uniform rotation. These results appear to rule out the hypothesis that the solar gravitational potential could have a large enough quadrapole term due to solar internal rotation to invalidate tests of general relativity.