Astron. Astrophys. 328, 670-681
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Wavelet analysis of solar activity recorded by sunspot groups
Peter Frick1, Denis Galyagin1, Douglas V.
Hoyt2, Elizabeth Nesme-Ribes3,*, Kenneth H. Schatten4, Dmitry Sokoloff5,
1 Institute of Continuous Media Mechanics,
Korolyov str.1, 614061 Perm, 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
November the 25th, 1996
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© European Southern Observatory (ESO) 1997
Online publication: November 24, 1997