Absolute solar EUV irradiances from the CELIAS/SEM during the long-term minimum of solar cycle 23

Authors: H. S. Ogawa, D. L. Judge, D. R. McMullin, and P. Gangopadhyay
Reference: AGU Fall Meeting, December 12, 1997, San Francisco, CA

Full-disk, solar EUV irradiances obtained by the CELIAS/SEM instrument aboard SOHO (in halo orbit at L-1) will be presented. All absolute fluxes presented have been normalized to the values at 1 AU. Solar EUV irradiances have been and are being continuously monitored during the solar cycle 23 minimum in two wavelength bands obtained by the CELIAS/SEM transmission grating spectrometer. The first-order band centered at the prominent solar He II emission line at 30 .4 nm is being monitored with an 8.0 nm band pass. The spectrometer's central -order monitors a broad wavelength band that covers a range from soft X-rays at about 0.1 nm to 77 nm in the EUV. Detailed analyses show that 35% of the central order signal is from the 0.1 to 8 nm wavelength region, 65% of the signal is from 15 to 50 nm, and less than 1% is from outside these two bands. The CELIAS/SEM data to be presented show significant long-term solar cycle and short-term intensity variations during this period.

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Last Update: April 2, 1999, James Weygand