How Different did the Solar UV Irradiance Evolve During the... Thierry Dudok de Wit , Gael Cessateur , Matthieu Kretzschmar

How Different did the Solar UV Irradiance Evolve During the Last Solar Cycle?
Thierry Dudok de Wit [] 1, Gael Cessateur1,2, Matthieu Kretzschmar1,
and Luis Vieira1
University of Orléans, France; 2Institute of Planetology and Astrophysics of Grenoble
(IPAG), France
Recent observations from SORCE/SIM suggest that during the last solar cycle the
spectral irradiance in the UV may have decreased by a factor larger than that observed during
the 2 previous cycles. This analysis, however, is complicated by the lack of continuous
observations and thus requires the stitching together of several records that do not always
Deland and Cebula [JGR, 2008] already built a single composite database by merging
different data observations. Here, we use a novel approach that allows to stitch these records
together in a self-consistent way [Dudok de Wit, A&A 2011], thereby providing improved
reconstructions of the last three solar cycles.
Using these new reconstructions we investigate the variability in the solar spectral
irradiance (amplitude, phase lag) for each cycle and assess how different the last one actually