The solar cycle variation in ultraviolet irradiance Original Research Article

The Solar Stellar Irradiance Comparison Experiment (SOLSTICE) is one of the ten science instruments on the Upper Atmosphere Research Satellite (UARS), launched in 1991 and now successfully operated for more than nine years. The SOLSTICE makes daily observations of solar spectral irradiance in the interval 120 to 320 nm — radiation important to ozone in the Earthʹs middle atmosphere. Nine years of SOLSTICE observations now provide a reliable estimate of solar-cycle variations, extending from early in 1992 near the peak of solar cycle 22, through solar minimum in late 1996, and now back to the high levels of solar cycle 23. These observations indicate almost a factor of two variation near Lyman-α (121.6 nm), decreasing to less than 10% near 200 nm, and to less than 1% near 300 nm.