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Context. The variability of Solar Spectral Irradiance over the rotationalperiod and its trend over the solar activity cycle are important forunderstanding the Sun-Earth connection as well as for observational constraintsfor solar models. Recently the SIM experiment on SORCE has published anunexpected negative correlation with Total Solar Irradiance of the visiblespectral range. It is compensated by a strong and positive variability of thenear UV range. Aims. We aim to verify whether the anti-correlatedSIM/SORCE-trend in the visible can be confirmed by independent observations ofthe VIRGO experiment on SOHO. The challenge of all space experiments measuringsolar irradiance are sensitivity changes of their sensors due to exposure tointense UV radiation, which are difficult to assess in orbit. Methods. Weanalyze a 10-year time series of VIRGO sun photometer data between 2002 and2012. The variability of Spectral Solar Irradiance is correlated with thevariability of the Total Solar Irradiance, which is taken as a proxy for solaractivity. Results. Observational evidence indicates that after six years onlyone single long-term process governs the degradation of the backup sunphotometer in VIRGO which is operated once in a month. This degradation can bewell approximated by a linear function over ten years. The analysis of theresiduals from the linear trend yield robust positive correlations of spectralirradiance at 862, 500 and 402 nm with total irradiance. In the analysis ofannual averages of these data the positive correlations change into weaknegative correlations, but of little statistical significance, for the 862 nmand 402 nm data. At 500 nm the annual spectral data are still positivelycorrelated with Total Solar Irradiance. The persisting positive correlation at500 nm is in contradiction to the SIM/SORCE results.

Correlation of Spectral Solar Irradiance with solar activity as measured by VIRGO