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Published October 1995 | Published
Journal Article Open

Reproduction of the Lyman α irradiance variability from analysis of full-disk images in the CaII K-line

Abstract

We have compared three years of daily CaII K-line images from the Big Bear Solar Observatory (BBSO) with HI Lymanα irradiance data from the Upper Atmosphere Research Satellite (UARS). The daily full-disk CaII K-line images are reduced to a new index of integrated excess emission, which reproduces both the 27 day rotational modulation and the solar cycle decrease in Lyα irradiance. Our analysis shows that while plages reproduce the 27-day variation quite well, the total K-line emission excess above the quiet background is needed to reproduce the secular solar cycle trend in the Lyα irradiance. The resulting K-line index exhibits a high degree of correlation (0.9) with the time series of measured Lyα flux.

Additional Information

© 1995 Kluwer Academic Publishers. Provided by the NASA Astrophysics Data System. Received 10 April, 1995; in revised form 10 July, 1995. The SOLSTICE and SUSIM data were provided courtesy of the NASA UARS project by Drs. Gary Rottman and Guenter Brueckner, respectively. We thank Dr. Judit Pap and Dr. Oran White for helpful discussions. This research is funded by the UARS Guest Investigator Program of NASA under grant NAG5-2782.

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