Contribution of Solar Chromospheric Fine Scale Features to UV Irradiance Variability

Details Contribution of Solar Chromospheric Fine Scale Features to UV Irradiance Variability Contribution of Solar Chromospheric Fine Scale Features to UV Irradiance Variability

Nov 2006

adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=2006ihy..worke..31k&link_type=abstract

2nd UN/NASA Workshop on International Heliophysical Year and Basic Space Science. Proceedings of the conference held 27 Novembe

Astronomy and Astrophysics

Astrophysics

Scientific paper

The Sun is the primary source of energy responsible for governing both the weather and climate of Earth. For that reason alone one would expect that changes in the amount and type of energy Earth received from the Sun could alter weather and climate on the Earth. The variations in the UV irradiance are produced by surface manifestation of solar magnetic activity. Considering the variations in the solar UV flux may cause significant changes in the Earth’s climate, understanding the physical origin of UV irradiance changes is an extremely important issue in Solar and Space Physics. We have segregated the (i) plages, (ii) magnetic network, and (iii) intranetwork + the background regions from the Call K spectroheliograms of 1980 and 1992, observed at the National Solar Observatory at Sacramento Peak, using their histograms taken for the full-disk. The different parameters like the intensity and area of the chromospheric features, the full-disk intensity (spatial K index), and the full width at half maximum (FWHM) of the histograms have been derived from the images. The spatial K index, FWHM, and the intensity of various features have been compared to the UV irradiance measured in the Mgll h and k lines by the Nimbus7 and NOAA9 satellites and it has been found that they are correlated with the Mgll h and k c/w ratio. We established, for the first time, from the results of 1992 images and of 1980 that the FWHM can be used as a good index for measuring and describing the chromospheric activity in the K-line. The results of both 1980 and 1992 images show an anticorrelation between the intensity and area of the network elements, which confirm the earlier findings derived entirely from different data set from Kodaikanal Call K spectroheliograms analyzed for the center of the solar disc in a quiet regions for a longer time interval of 1951 to 1983 (Kariyappa and Sivaraman, 1994). During solar minimum the network is fainter but covers a larger area than during solar maximum. These results suggest that the variations in both the intensity and area of the various chromospheric features have to be taken into account in irradiance models.

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