The Source Function in a Non-Equilibrium Atmosphere. II. The Depth Dependence of the Source Function for Resonance and Strong Subordinate Lines.

Abstract

We obtain an algebraic solution for the depth variation of the source function 8L (r) for resonance and strong subordinate lines by using the Eddington approximation plus the method of discrete ordinates. We show that if an observed line profile, produced in an atmosphere with the above SL (r), is analyzed under the assumption of local thermodynamic equilibrium, an underestimate of T.(r) in the outer atmospheric layer results. The derived SL(r) agrees in qualitative behavior with the source function found empirically by Athay and Thomas for the early Balmer lines of hydrogen.