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


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Wavelet entropy as a measure of solar cycle complexity

S. Sello

Mathematical and Physical Models, Enel Research, Via Andrea Pisano 120, 56122 Pisa, Italy (sello@pte.enel.it)

Received 10 March 2000 / Accepted 11 May 2000

Abstract

Using wavelet analysis approach, we can derive a measure of the disorder content of solar activity, following the temporal evolution of the so-called wavelet entropy . The interesting feature of this parameter is its ability to extract a dynamical complexity information, in terms of frequency distribution of the energy content, avoiding restrictions, common in the nonlinear dynamics theory, such as stationarity. The analysis is performed on the monthly time series of sunspot numbers. From the time behaviour of the wavelet entropy we found a clear increase in the disorder content of solar activity for the current [FORMULA] solar cycle. This result suggests general low accuracies for current solar cycle prediction methods. Moreover, we pointed out a possible connection between wavelet entropy behaviour and solar excursion phases of solar dipole.

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


© European Southern Observatory (ESO) 2000

Online publication: December 5, 2000

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