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Astron. Astrophys. 332, 1082-1086 (1998)

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Long-term behavior of emission from solar faculae: steps towards a robust index

M. Fligge and S.K. Solanki

Institute of Astronomy, ETH-Zentrum, CH-8092 Zürich, Switzerland

Received 29 May 1997 / Accepted 8 January 1998


Facular emission is one of the major contributors to long-term solar irradiance variations. Reconstructions of past facular variations, however, are strongly hampered by the lack of reliable proxies, particularly on time-scales longer than a solar cycle. We consider the five potential facular proxies with records covering more than 40 years. By suitably weighting and combining them we create a new proxy. In comparison with sunspot relative number the combined proxy exhibits enhanced values during solar cycles 16 and 17. This suggests that the Sun may have been brighter during those cycles than earlier models, which used sunspot numbers as the facular proxy, indicate.

Key words: Sun: activity – Sun: faculae, plages – solar-terrestrial relations – sunspots

Send offprint requests to: M. Fligge

© European Southern Observatory (ESO) 1998

Online publication: March 30, 1998