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A 10-year set of Ca II k-line filtergrams

Johannesson, Anders and Marquette, William H. and Zirin, Harold (1998) A 10-year set of Ca II k-line filtergrams. Solar Physics, 177 (1-2). pp. 265-278. ISSN 0038-0938. doi:10.1023/a:1004940227692.

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We have processed a 10-year set of BBSO Caii K-line filtergrams covering most of solar cycle 22. The excess K-line emission is integrated to form linear and square-root activity indices that are fitted to UV data from UARS and SME. Good fits are found both for the Mgii core–wing ratio (linear) and total Lα irradiance (square root) and the indices are thus good proxies for UV data. The SME Lα irradiance is systematically lower by 20% than predicted from our corresponding K-line indices. The 10.7 cm radio data confirms that SME underestimated the flux. The network is partly responsible for the solar cycle variation of the indices and is relatively more important in Lα than in Mgii and Caii K. This is due to the saturation of Lα equivalent width. We also report on substantial improvements to the equipment and reduction software. The system is now based on a digital CCD camera which promises more accurate measurements in the upcoming solar cycle 23.

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Additional Information:© 1998 Kluwer Academic Publishers. Received 22 November 1996; accepted 19 May 1997. The UARS data were provided courtesy of the NASA UARS project by Drs. Gary Rottman and Guenter Brueckner. This research is funded by the Upper Atmosphere Research Program of NASA under grant NAG52782. The purchase and installation of the new camera and the new optical layout were funded by grant NSF ATM9303508 of the RISE program. We are indebted to Dr. H. Lin for providing flatfielding software. SME satellite data are courtesy of the University of Colorado. The 10.7 cm radio flux data are provided by the National Research Council of Canada. We also thank Drs. Oran White, Judith Lean and Judit Pap for helpful discussions. HZ wishes to dedicate his participation in this paper to an anonymous NSF referee who predicted, ‘We will never see digital data from the Big Bear Solar Observatory.’
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Subject Keywords:Solar Cycle, Activity Index, Substantial Improvement, Equivalent Width, Good Proxy
Issue or Number:1-2
Record Number:CaltechAUTHORS:20200810-134515447
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Official Citation:Johannesson, A., Marquette, W.H. & Zirin, H. A 10-Year Set of Ca II K-Line Filtergrams. Solar Physics 177, 265–278 (1998).
Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:104885
Deposited By: Rebecca Minjarez
Deposited On:20 Oct 2020 18:14
Last Modified:16 Nov 2021 18:37

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