New Measure for Estimating Solar Radiation
A new measure for estimating solar radiation from the ultraviolet "glow" of
the upper atmosphere will allow scientists an additional tool for better
understanding the connections between solar and terrestrial variability.
Strickland et al. [Solar EUV irradiance variability derived from
terrestrial far ultraviolet dayglow observations] define a new physical
quantity for measuring the short wavelength (extreme ultraviolet/soft
X-ray) solar radiation energy that excites gases in the upper atmosphere,
producing emissions known as far ultraviolet dayglow and maintaining the
sunlit ionosphere. The measure, which the authors denote as QEUV, can also
provide an independent assessment of direct measurements and models of
solar EUV energy. Using ultraviolet dayglow observations from the GUVI
instrument on the TIMED spacecraft for nearly a month in 2002, the
researchers showed that QEUV closely tracks the solar EUV measurements of
the SEM instrument on the SOHO spacecraft during the Sun's rotation and
during numerous spikes arising from solar flares. They suggest that their
findings contradict recent reports that solar EUV radiation at its shorter
wavelengths is underreported by as much as a factor of four.
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