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Astron. Astrophys. 328, 670-681 (1997)

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Wavelet analysis of solar activity recorded by sunspot groups

Peter Frick 1, Denis Galyagin 1, Douglas V. Hoyt 2, Elizabeth Nesme-Ribes * 3, Kenneth H. Schatten 4, Dmitry Sokoloff 5, and Viktor Zakharov 1

1 Institute of Continuous Media Mechanics, Korolyov str.1, 614061 Perm, Russia
2 Research and Data Syatem Corporation, 78 55 Walker Drive, Suite 460, Greenbelt, MD 20770, USA
3 CNRS URA 326, Observatoire de Paris, 5 Place Janssen, F-92195 Meudon, France
4 NASA/Goddard Space Flight Center, Gde 914, Greenblelt, MD 20771, USA
5 Department of Physics, Moscow State University, 119899 Moscow, Russia

Received 22 September 1995 / Accepted 14 May 1996


The wavelet transform of monthly sunspot group data from 1610 to 1994 is investigated. Only two pronounced peaks corresponding to the Schwabe and the Gleissberg cycles, are present in this transform. The wavelet analysis of the time-series also shows the Maunder and Dalton minima as well as a deviation in the cycle length around 1900. The variations in the periodicity of the main 11 year cycle are studied. We show that all the minima of this cycle occur when the derivative of cycle length as a function of time is negative. Cycles of greater duration are connected with periods of weak solar activity. While the sunspot group number was periodic at the end of the Maunder minimum, it did not seem to follow any periodic behavior during the main part of this minimum. The abrupt transition between normal and Maunder minimum cycles is present in the sunspot group data.

Key words: Sun: activity – sunspots – methods: data analysis

* Deceased on November the 25th, 1996

Send offprint requests to: D. Sokoloff


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© European Southern Observatory (ESO) 1997

Online publication: March 26, 1998