Solar Soft X-ray Variability During the SORCE Mission

Authors: Tom Woods and Gary Rottman
Affiliation: LASP, University of Colorado

The SORCE satellite was launched in January 2003, and the solar activity has evolved from near solar maximum conditions to moderate activity during the SORCE mission in 2003. The XUV Photometer System (XPS) aboard SORCE measures the soft X-ray, or XUV, energy input to Earth's atmosphere. The XPS instrument is measuring the solar XUV irradiance with 7-10 nm resolution shortward of 34 nm and the bright hydrogen emission at 121.5 nm. The solar irradiance varies on all time scales, seconds to years, and this variation is very dependent on wavelength. During the SORCE mission, the XPS instrument has observed several flares which last from minutes to hours and over 10 solar rotations which have a period of about 27 days. The XUV radiation, being mostly from coronal emissions, varies more than any other wavelength in the solar spectrum. The XPS measurements indicate variations by a factor of 10 for the larger flares and a factor of about 2 for solar rotation. The variations of the solar XUV irradiance will be discussed in the context of the SORCE mission.