Solar Physics Division Meeting 2000, June 19-22
Session 2. Corona, Solar Wind, Flares, CMEs, Solar-stellar, Instrumentation, Other
Display, Chair: J. Krall, Monday-Thursday, June 19, 2000, 8:00am-6:00pm, Forum Ballroom

## [2.114] EUV irradiance variations measured with the SOHO Coronal Diagnostic Spectrometer

P. Brekke (ESA Space Science Dept., NASA Goddard SFC), W.T. Thompson (SM&A Corp., NASA Goddard SFC)

The Coronal Diagnostic Spectrometer aboard the Solar and Heliospheric Observatory observes the solar EUV spectrum in two bands between 308--379~{Å} and 513--633~{Å}. The full Sun irradiance can be measured by rastering the instrument over the solar disk. Measurements of the solar irradiance have been made starting 25~March 1997 and continuing to the present, ranging from very quiet to very active Sun. These measurements are the only current EUV spectral irradiance measurements taken on a regular basis. As well as irradiance values, the most recent observations also provide moderate resolution solar images to help quantify the important sources of the irradiance variability. The dependence of individual spectral lines on the solar cycle is presented, spanning the temperature range from 3 \times 104~K to 2.7 \times 106~K. The important spectral lines of He~II and Si~XI at 304~{Å} are observed in second order and separated. The high spectral resolution of these measurements, combined with the coverage of a significant proportion of the solar cycle, provide a unique dataset for understanding solar variability in the EUV. In addition, these data are important input for interpreting data from broadband and lower resolution irradiance monitors, such as the SOHO SEM and TIMED.