Volume 431, Number 2, February IV 2005
|Page(s)||L5 - L8|
|Published online||04 February 2005|
Letter to the Editor
The periodic behaviour of the North-South asymmetry of sunspot areas revisited
Departament de Física, Universitat de les Illes Balears, 07122 Palma de Mallorca, Spain e-mail: [dfsjlb0;ramon.oliver]@uib.es
2 Departament de Matemàtiques i Informàtica, Universitat de les Illes Balears, 07122 Palma de Mallorca, Spain e-mail: firstname.lastname@example.org
Accepted: 23 December 2004
Up to now, the periodic behaviour of the N-S asymmetry of solar activity has been analyzed by applying the power spectrum analysis to the time series generated from a normalized definition of the asymmetry. Using sunspot areas and the properties of the discrete Fourier transform, we show that the use of the normalized time series leads to misleading results, and that the correct asymmetry time series to be used is generated from the difference between the values of solar activity indicators in the Northern and Southern solar hemispheres. However, in this case the found significant periodicities correspond to periodicities already present in the hemispheric sunspot areas time series, not providing with any interesting information about the asymmetric behaviour of the solar activity. Of course, our conclusions are extensive to all the studies of the periodic behaviour of the N-S asymmetry of solar activity time series computed by means of the normalized definition of the asymmetry, and independent of the considered solar activity feature.
Key words: Sun: activity / Sun: sunspots / methods: data analysis / methods: statistical
© ESO, 2005
Current usage metrics show cumulative count of Article Views (full-text article views including HTML views, PDF and ePub downloads, according to the available data) and Abstracts Views on Vision4Press platform.
Data correspond to usage on the plateform after 2015. The current usage metrics is available 48-96 hours after online publication and is updated daily on week days.
Initial download of the metrics may take a while.