Solar O_I 1304-Å triplet line profiles

Estimates are made for the full-disk line profiles of the solar O_I resonance triplet at 1304 Å using data from experiments on Solar Maximum Mission and Orbiting Solar Observatory 8. The observed profiles are considerably self-reversed, and an accurate approximation to the actual line profiles using the sum of two equal and offset Gaussian profiles is presented. The set of observations, though sparse, cover the period of time from 1975 to 1985. The solar cycle variation of total O_I 1304-Å flux is ∼30% (as determined from rocket and Solar Mesophere Explorer observations), but no solar cycle variation is apparent in the line shapes above the level of day-to-day variability. In addition, the fraction of the total flux carried in each component line of the triplet was also approximately constant during the last solar cycle. The derived full-disk line shape parameters may be used, when combined with an appropriate value for the line-integrated full-disk solar flux, in the analysis of planetary or cometary O_I 1304-Å observations under any solar conditions.