Short-Term Temporal Variations of Nimbus-7 Measurements of the Solar UV Spectral Irradiance

摘要

NIMBUS-7 measurements of the solar spectral irradiance in the 160-400 nm range during November 7, 1978 - October 29, 1984, were analyzed to determine the characteristics of their short-term variations (days and weeks to a couple of months). The persistence of solar-rotational variations is shown to be uniformly high for the UV wavelengths important for inducing stratospheric photochemical reactions and for heating the stratosphere, which contrasts greatly with the low and nonuniform persistence for coronal EUV wavelengths and the standard ground-based measures of solar variability, the Ottawa 10.7 cm flux (F10) and sunspot number (R). Periodicity in the 13 - 14 day range is the second strongest short-term variation (27 - 28 day solar rotational variations are the strongest short-term periodicity). The ratios of power in the 13-day periodicity to that in the 27-day periodicity is fairly constant for photospheric UV fluxes throughout the 170 - 260 nm wavelength range, the main exception being the chromospheric Si II lines in the 180 - 182 nm range.