High-Resolution Observations of the Solar Hydrogen Lyman Lines in the Quiet Sun with the SUMER Instrument on SOHO

We present high-resolution observations of the higher H Lyman series lines taken with the Solar Ultraviolet Measurements of Emitted Radiation (SUMER) experiment flown on the Solar and Heliospheric Observatory (SOHO) spacecraft. We have used systematic observations extending from disk center to the solar limb to compute average profiles for representative solar features of the quiet Sun, limb-brightening curves, and full-disk, quiet-Sun profiles for Ly? through Ly?(11) and the Lyman continuum. The effects of radiative transfer are apparent in all of the line profiles we studied. The average quiet-Sun profiles for Ly? through Ly are self-reversed, and the remaining lines are flat-topped. The characteristics of the line profiles vary markedly with intensity. We observe strong enhancements in the red wings of network profiles, while the faint cell-center profiles are nearly symmetric. We also find that the intensities of the H Lyman lines increase at the limb, although the limb brightening is weak compared to optically thin transition region emission lines and largely obscured by the intensity variations observed in the quiet Sun.

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