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Observed solar UV irradiance variations of importance to middle atmosphere energetics and photochemistryAbsorption of solar UV irradiance in the spectral interval 120-420 nm is chiefly responsible for radiative heating and photodissociation of important atmospheric constituents (e.g., O2, O3, H2O, NO2, etc.) in the stratosphere, mesosphere, and lower thermosphere. Thus, the absolute value and time perturbations of the UV irradiance could significantly affect the energetics, photochemistry, and subsequent dynamics of these regions. Analysis of preliminary data from the SOLSTICE (UARS) observations for a period of 244 days (3 Oct 1991-2 Jun 1992) is discussed in this paper. The data provide mean daily values of the spectral distribution of the observed irradiances at 1-nm resolution and their solar rotation and semirotation variations. The average amplitudes of the 27-day irradiance oscillations for the 244-day data period were 5.7% at Lyman-alpha (121 nm), 1% at 200 nm, 0.5% at 210 nm, and generally less than 0.2% at wavelengths longer than 280 nm. The average amplitudes of 13.5-day oscillations were, by and large, about half of these values. Solar irradiance variations at 10.7 cm are highly correlated with those at Ly-alpha and other chromospheric emission lines (r = 0.7 to 0.8) and only moderately correlated with irradiances at wavelengths of 180-208 nm (r = 0.5). The correlation decreases as the source region of the irradiance gets closer to the base of the photosphere. At the 2-nm interval 279-281 nm, however, which contains the cores of the Mg II h and k lines, the correlation is again approximately 0.8.
Document ID
19950028984
Acquisition Source
Legacy CDMS
Document Type
Reprint (Version printed in journal)
Authors
London, Julius
(Colorado Univ. Boulder, CO, US, United States)
Date Acquired
August 16, 2013
Publication Date
September 1, 1994
Publication Information
Publication: Advances in Space Research
Volume: 14
Issue: 9
ISSN: 0273-1177
Subject Category
Geophysics
Accession Number
95A60583
Funding Number(s)
CONTRACT_GRANT: NAS5-27263
Distribution Limits
Public
Copyright
Other

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