RADIATION-HYDRODYNAMIC WAVES IN AN OPTICALLY GREY ATMOSPHERE .2. ANALYSIS OF WAVE PROPERTIES AND EFFECTS OF THERMAL-CONDUCTIVITY IN A HOMOGENEOUS MODEL

The properties of radiation-hydrodynamic waves in a radiative, thermal ly conducting, uniform atmosphere are investigated, avoiding the Eddin gton approximation and considering a temporal as well as a spatial ana lysis. The analysis of the dispersion equation shows the existence of acoustic, radiation, and thermal wave modes and a relaxation mode as w ell. The generalized Spiegel formula is discussed and the accuracy of the Eddington approximation for the radiation-hydrodynamic waves is co nsidered. The amplitudes and phases of disturbances of gas and radiati on pressure, intensity, and temperature are obtained for standing and travelling waves and for the relaxation mode too. The polar angle depe ndence of the phase shift between velocity and intensity is investigat ed. The predictions for full-disk intensity observations and the defic iencies of earlier, less complete approaches are discussed.