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Astron. Astrophys. 363, 311-315 (2000)

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1. Introduction

Multiscale analysis, based on the wavelet approach, has been successfully used for many different physical applications, including global solar activity (Ochadlick et al. 1993; Lawrence et al. 1995). Intermittence features have been well analysed through the use of a continuous wavelet transforms on the monthly sunspot numbers time series. More recently, different authors used longer daily sunspot numbers time series to investigate more accurately new subtle periodicities and their evolutions (Frick et al. 1997; Ballester et al. 1999; Fligge et al. 1999; Sello 2000). A recent work on wavelet applications to biomedical signals, shows the utility of a new parameter, derived from wavelet formalism, to quantify the degree of disorder in the time series. This quantity, called wavelet entropy , essentially gives an information on the scales extension involved in the energy distribution, i.e. a dynamical complexity parameter (Quian Quiroga et al. 1999). The main aim of the present work is the application of the wavelet entropy approach to the solar activity, through the wavelet analysis of the monthly mean sunspot numbers.

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© European Southern Observatory (ESO) 2000

Online publication: December 5, 2000