The Solar Cycle in the Extreme Ultraviolet
Session 25 -- Solar System and Heliosphere
Oral presentation, Wednesday, January 12, 10:15-11:45, Salon VI Room (Crystal Gateway)

[25.06] The Solar Cycle in the Extreme Ultraviolet

W D Pesnell (ARC), W R Hoegy (NASA/GSFC)

We present Pioneer Venus Orbiter observations of the solar EUV flux. The 13 years of measurements cover the last part of Solar Cycle 21 and the majority of Solar Cycle 22. The Ipe flux is a direct measure of the solar EUV flux that correlated extremely well with earth based measurements until the onset of Solar Cycle 22. We demonstrate this correlation with the 10.7 cm. radio flux and ionospheric conditions. Our measurements show that Solar Cycle 22 was one of the most active ever recorded. The Ipe flux is a yield-weighted integration over wavelengths from 100 \AA\ to 1300 \AA. It is dominated by emission in L${}_\alpha$ $\lambda$1216, with roughly 50\% of the flux coming from the remaining wavelengths. Other EUV proxy measurements are compared to the Ipe flux.