Variability in the solar constant from irradiances shortward of Lyman-Alpha Original Research Article

The variation in the solar constant, S(t), is reproduced by the SOLAR2000 Research Grade v1.05 empirical solar irradiance model and is described for 5 solar cycles between cycles 18 and 23 (February 14, 1947 through May 31, 2000). This solar constant variation is dependent upon the derivation data sets and the formulation of SOLAR2000 which are described in more detail. The S(t) temporal variability in SOLAR2000 is shown for the solar spectrum between 1–122 nm. The variability is consistent with previous discussions in the literature and a new result is shown where the 1–122 nm wavelength range accounts for about 5–14% of the standard deviation reported in the ASTM E-490 standard. The minimum-maximum range of S(t) variation due to 1–122 nm variability is between 1367.2768 Wm−2 on 1986-152 and 1367.2877 Wm−2 on 1957-340. The mean S(t) in these data is 1367.2796 Wm−2.