The solar hydrogen Lyman alpha to Lyman beta line ratio

Aims. We investigate the variation in the solar hydrogen Lyman alpha (Ly alpha) to Lyman beta (Ly beta) line ratio as a function of the solar activity by taking into account new results obtained by SoHO/SUMER and TIMED/SEE. Methods. We reanalyze data of quiet and active regions previously collected with the LPSP multichannel instrument on OSO8. We then re-examine data obtained on the solar disk with SUMER and compare them with previous data. In a second step, we use the full Sun H I Ly beta profiles to determine the Ly beta contribution to the SEE profiles obtained with a 0.4 nm full width at half-maximum. The variation in the Ly alpha to Ly beta line ratio is then measured for part of the solar cycle 23 (2002-2008). Results. We determine the radiance line ratio of the solar H I Ly alpha to Ly beta line for a quiet Sun area and the relation between the ratio of the Ly alpha to Ly beta irradiance and the Ly alpha solar irradiance.