Measurements of the solar soft x-ray irradiance from the Student Nitric Oxide Explorer

Beginning on March 11, 1998, the Student Nitric Oxide Explorer (SNOE) satellite has made daily observations of the solar soft x-ray irradiance. These measurements are carried out by a multi-channel photometer system utilizing x-ray sensitive photodiodes with individual thin film filters. Current from the photodiodes is analyzed in terms of a solar reference spectrum in order to determine solar irradiances. The irradiances from 2 to 10 nm vary between 0.15 and 0.40 ergs cm(-2) s(-1) from March 11 to July 19, 1998 while the solar 10.7 cm fluxes varied between 85 and 140 x10(-22) W m(-2) Hz(-1). A 27-day periodicity is observed with variations in the soft x-ray irradiance on the order of a factor of two. The measured irradiances are shown to be correlated with the solar 10.7 an flux but only mildly so with the GOES-8 0.1 to 0.8 nm solar fluxes.