Variations of solar ultraviolet irradiance observed by the UARS SOLSTICE - 1991 to 1999

The Solar Stellar Irradiance Comparison Experiment (SOLSTICE) is one of ten instruments on the Upper Atmosphere Research Satellite (UARS) - one of two instruments measuring the solar ultraviolet irradiance. The instrument is a three channel spectrometer covering the spectral range 120 to 420 nm with a spectral resolution of approximately 0.2 nm. It has been successfully operating since October 1991, and has now provided more than eight years of data, extending from near the peak of solar cycle 22, through solar minimum and into the new cycle. The data provide time series that display solar variations over time scales from a few days up to the 11-year solar cycle. Quantitative estimates of amplitudes of both rotational modulation and the solar cycle variation in the 1991-1999 epoch are given for the UV spectrum between 119 and 300 nm.