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18 months of UV irradiance observations from the Solar Mesosphere Explorer
Author(s) -
London Julius,
Bjarnason Gudmundur G.,
Rottman Gary J.
Publication year - 1984
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/gl011i001p00054
Subject(s) - irradiance , solar irradiance , mesosphere , atmospheric sciences , solar rotation , stratosphere , wavelength , environmental science , solar maximum , physics , range (aeronautics) , flux (metallurgy) , solar physics , solar cycle , optics , astrophysics , materials science , quantum mechanics , solar wind , magnetic field , composite material , metallurgy
Daily solar irradiance measurements in the spectral interval 120‐305 nm have been made since 6 October 1981 with an instrument on the Solar Mesosphere Explorer. The instrument operates with a spectral resolution of about 0.75 nm. Analysis of the observed data for the period 6 December 1981 to 3 June 1983 (20 solar rotations) shows that during this period there was an apparent decrease in irradiance at all wavelengths observed (−19.7% ± 9.7% at Ly‐α) but the decrease was not significantly different from zero at wavelengths longer than 210 nm. The cross correlations between daily values of the solar irradiance and 10.7 cm flux varied from 0.7 (Ly‐α) to 0.5 (210‐215 nm) and ∼0 (290‐295nm). Calculations of the % range (i.e., highest to lowest value) of the irradiance within each solar rotation showed that for Ly‐α the range varied between 6% and 30% over the 20 solar rotations studied. At longer wavelengths the % range was smaller—about 7% at 180 nm and about 2% beyond 240 nm. The percent range values indicate representative variations useful as input data for model calculations of stratosphere/mesosphere responses to short period solar variability.