Radiation loss rates in Lyman-alpha for solar conditions

Mean radiation loss rates per unit volume in Lyman-alpha are computed for solar conditions as a function of the optical thickness of the radiating region. No significant corrections to the optically thin coronal approximation are found until the Lyman-alpha optical thickness at line center exceeds 100. At larger optical thicknesses the corrections can be large as a result of the increased ionization of hydrogen from absorptions in the Balmer continuum. The correction suggested by McClymont and Canfield (1983) is found to be too large for most solar applications.