HOW ACTIVE WAS SOLAR CYCLE-22

Solar EUV observations from the Langmuir probe on Pioneer Venus Orbite r suggest that at EUV wavelengths solar cycle 22 was more active than solar cycle 21. The Langmuir probe, acting as a photodiode, measured t he integrated solar EUV flux over a 13 1/2 year period from January 19 79 to June 1992, the longest continuous solar EUV measurement. The Ipe EUV flux correlated very well with the SME measurement of L(alpha) du ring the lifetime of SME and with the UARS SOLSTICE L(alpha) from Octo ber 1991 to June 1992 when the Ipe measurement ceased. Starting with t he peak of solar cycle 21, there was good general agreement of Ipe EUV with the 10.7 cm, Ca K, and He 10830 solar indices, until the onset o f solar cycle 22. From 1989 to the start of 1992, the 10.7 cm flux exh ibited a broad maximum consisting of two peaks of nearly equal magnitu de, whereas Ipe EUV exhibited a strong increase during this time perio d making the second peak significantly-higher than the first. The only solar index that exhibits the same increase in solar activity as Ipe EUV and L(alpha) during the cycle 22 peak is the total magnetic flux. The case for high activity during this peak is also supported by the p resence of very high solar flare intensity.