AN ASYMPTOTIC DESCRIPTION OF SOLAR ACOUSTIC-OSCILLATION OF LOW AND INTERMEDIATE DEGREE

We present an asymptotic description of high-frequency solar p modes w hich permits an accurate treatment of regions where the seismic parame ters vary rapidly with depth, and incorporates the strong effect of gr avity perturbations on low-degree modes. The description is based on a n asymptotic reduction of the governing fourth-order system of linear differential equations to second order. Approximate solutions of the s econd-order equation are then developed using a Born-type asymptotic e xpansion. The accuracy of the resulting description is tested numerica lly on a standard solar model. Higher order Born approximations give f ractional accuracies of at least 10(-3). This is approximately an orde r of magnitude better than results from an earlier, more straightforwa rd second-order analysis by Vorontsov.