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Sunspot and Group Number: Recent advances from historical data

Published online by Cambridge University Press:  03 March 2020

Frédéric Clette ,
José M. Vaquero ,
María Cruz Gallego  and
Laure Lefèvre
Frédéric Clette
Affiliation:
Royal Observatory of Belgium, 3, avenue Circulaire, 1180 Brussels, Belgium email: frederic.clette@oma.be
José M. Vaquero
Affiliation:
Departamento de Fsica, Universidad de Extremadura, 06071 Mérida, Spain
María Cruz Gallego
Affiliation:
Departamento de Fsica, Universidad de Extremadura, 06071 Badajoz, Spain
Laure Lefèvre
Affiliation:
Royal Observatory of Belgium, 3, avenue Circulaire, 1180 Brussels, Belgium email: frederic.clette@oma.be
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Abstract

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Due to its unique 400-year duration, the sunspot number is a central reference for understanding the long-term evolution of solar activity and its influence on the Earth environment and climate. Here, we outline current data recovery work. For the sunspot number, we find historical evidence of a disruption in the source observers occurring in 1947–48. For the sunpot group number, recent data confirm the clear southern predominance of sunspots during the Maunder Minimum, while the umbra-penumbra ratio is similar to other epochs. For the Dalton minimum, newly recovered historical observations confirm a higher activity level than in a true Grand Minimum.

Keywords

Sun: sunspotsSun: photosphereSun: activitymethods: data analysishistory of astronomy
Type
Contributed Papers
Information
Proceedings of the International Astronomical Union , Volume 14 , Symposium A30: Astronomy in Focus XXX , August 2018 , pp. 156 - 159
Copyright
© International Astronomical Union 2020

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