AN ASYMPTOTIC DESCRIPTION OF SOLAR ACOUSTIC-OSCILLATIONS WITH AN ELEMENTARY EXCITATION SOURCE

We extend the asymptotic description of solar p-modes to include an ex citation source. The linear dynamic response of a star is considered w ithin the general framework of a Fourier transform of the source funct ion in time, and a vector spherical harmonic decomposition in space. Q uantitative analysis is developed for the linear response to an 'eleme ntary' harmonic excitation source described by a delta-function in the radial direction, using a simplified description of the energy leakag e from the acoustic cavity. The synthetic p-mode power spectra are com puted numerically for different depths of the excitation source, and t heir simple properties are discussed. The asymptotic eigenfrequency eq uation is generalized to describe the frequencies of maximum amplitude s in the theoretical response function. The resulting frequency equati on with modified 'surface phase shift' degenerates into the standard e igen-frequency equation at low frequencies, and describes the high-fre quency 'pseudomodes' in the high-frequency limit, joining both these w ell-known theoretical descriptions in the intermediate frequency range .