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How active was solar cycle 22?
Author(s) -
Hoegy W. R.,
Pesnell W. D.,
Woods T. N.,
Rottman G. J.
Publication year - 1993
Publication title -
geophysical research letters
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 2.007
H-Index - 273
eISSN - 1944-8007
pISSN - 0094-8276
DOI - 10.1029/93gl01453
Subject(s) - extreme ultraviolet lithography , solar cycle 22 , solar cycle , solar maximum , solar minimum , physics , solar irradiance , atmospheric sciences , flux (metallurgy) , solar cycle 23 , extreme ultraviolet , solar cycle 24 , environmental science , astrophysics , optics , solar wind , materials science , plasma , laser , quantum mechanics , metallurgy
Solar EUV observations from the Langmuir probe on Pioneer Venus Orbiter suggest that at EUV wavelengths solar cycle 22 was more active than solar cycle 21. The Langmuir probe, acting as a photodiode, measured the integrated solar EUV flux over a 13 1/2 year period from January 1979 to June 1992, the longest continuous solar EUV measurement. The Ipe EUV flux correlated very well with the SME measurement of L α during the lifetime of SME and with the UARS SOLSTICE L α from October 1991 to June 1992 when the Ipe measurement ceased. Starting with the 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 of solar cycle 22. From 1989 to the start of 1992, the 10.7 cm flux exhibited a broad maximum consisting of two peaks of nearly equal magnitude, whereas Ipe EUV exhibited a strong increase during this time period 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 α during the cycle 22 peak is the total magnetic flux. The case for high activity during this peak is also supported by the presence of very high solar flare intensity.