The statistical significance of the N-S asymmetry of solar activity revisited

Abstract

The main aim of this study is to point out the difficulties found when trying to assess the statistical significance of the North-South asymmetry (hereafter SSNSA) of the most usually considered time series of solar activity. First of all, we distinguish between solar activity time series composed by integer or non-integer and dimensionless data, or composed by non-integer and dimensional data. For each of these cases, we discuss the most suitable statistical tests which can be applied and highlight the difficulties to obtain valid information about the statistical significance of solar activity time series. Our results suggest that, apart from the need to apply the suitable statistical tests, other effects such as the data binning, the considered units and the need, in some tests, to consider groups of data, affect substantially the determination of the statistical significance of the asymmetry. Our main conclusion is that the assessment of the statistical significance of the N-S asymmetry of solar activity is a difficult matter and that an absolute answer cannot be given, since many different effects influence the results given by the statistical tests. In summary, the quantitative results about the statistical significance of the N-S asymmetry of solar activity provided by different authors, as well as the studies about its behaviour, must be considered with care because they depend from the chosen values of different parameters or from the considered units.

arXiv commentAstronomy and Astrophysics Latex, 9 pages, 4 figures

References in corpus (3)

• Hemispheric Sunspot Numbers R_n and R_s: Catalogue and N-S asymmetry analysis
• Statistical analysis of solar H-alpha flares
• The north-south asymmetry of soft X-ray flare index during solar cycles 21, 22 and 23

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• Photospheric Magnetic Field: Relationship Between North-South Asymmetry and Flux Imbalance
• The Phase Shifts of the Paired Wings of Butterfly Diagrams
• Comparison of Latitude Distribution and Evolution of Even and Odd Sunspot Cycles
• The Extended Solar Cycle and Asymmetry of the Large-Scale Magnetic Field
• Comparison of the shape and temporal evolution of even and odd solar cycles
• Long-term Pulses of Dynamic Coupling between Solar Hemispheres
• Hemispheric analysis of the magnetic flux in regular and irregular solar active regions