The interpretation of absorption-line shifts in the solar spectrum

The shifts of Fraunhofer lines of different chemical elements in a homogeneous medium with a plane monochromatic progressive adiabatic sound waves are derived. The calculations indicate that lines of neutral elements (6 ₀ 14) with lower excitation potentials ₀ i= 0–2 eV are red shifted, those with excitation potential ₀ i= 4–12 eV are blue shifted, and with ₀ i= 3 eV are both blue and red shifted. The lines of ions are shifted toward the blue. The shifts of Fraunhofer lines are found to decrease from the centre of the solar disk to the limb. These results agree qualitatively and quantitatively with observations.