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Nonlinear Processes in Geophysics An interactive open-access journal of the European Geosciences Union
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Volume 21, issue 6
Nonlin. Processes Geophys., 21, 1113–1126, 2014
https://doi.org/10.5194/npg-21-1113-2014
© Author(s) 2014. This work is distributed under
the Creative Commons Attribution 3.0 License.

Special issue: Complex network approaches to analyzing and modeling nonlinear...

Nonlin. Processes Geophys., 21, 1113–1126, 2014
https://doi.org/10.5194/npg-21-1113-2014
© Author(s) 2014. This work is distributed under
the Creative Commons Attribution 3.0 License.

Research article 24 Nov 2014

Research article | 24 Nov 2014

Long-term changes in the north–south asymmetry of solar activity: a nonlinear dynamics characterization using visibility graphs

Y. Zou1,2,3, R. V. Donner3,4, N. Marwan3, M. Small5, and J. Kurths3,6,7 Y. Zou et al.
  • 1Department of Physics, East China Normal University, 200062 Shanghai, China
  • 2State Key Laboratory of Theoretical Physics, Institute of Theoretical Physics, Chinese Academy of Sciences, Beijing 100190, China
  • 3Potsdam Institute for Climate Impact Research, P.O. Box 60 12 03, 14412 Potsdam, Germany
  • 4Max Planck Institute for Biogeochemistry, Hans-Knöll-Str. 10, 07745 Jena, Germany
  • 5School of Mathematics and Statistics, University of Western Australia, Crawley, WA 6009, Australia
  • 6Department of Physics, Humboldt University Berlin, Newtonstr. 15, 12489 Berlin, Germany
  • 7Institute for Complex Systems and Mathematical Biology, University of Aberdeen, Aberdeen, AB243UE, UK

Abstract. Solar activity is characterized by complex dynamics superimposed onto an almost periodic, approximately 11-year cycle. One of its main features is the presence of a marked, time-varying hemispheric asymmetry, the deeper reasons for which have not yet been completely uncovered. Traditionally, this asymmetry has been studied by considering amplitude and phase differences. Here, we use visibility graphs, a novel tool of nonlinear time series analysis, to obtain complementary information on hemispheric asymmetries in dynamical properties. Our analysis provides deep insights into the potential and limitations of this method, revealing a complex interplay between factors relating to statistical and dynamical properties, i.e., effects due to the probability distribution and the regularity of observed fluctuations. We demonstrate that temporal changes in the hemispheric predominance of the graph properties lag those directly associated with the total hemispheric sunspot areas. Our findings open a new dynamical perspective on studying the north–south sunspot asymmetry, which is to be further explored in future work.

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We use visibility graphs to characterize asymmetries in the dynamics of sunspot areas in both solar hemispheres. Our analysis provides deep insights into the potential and limitations of this method, revealing a complex interplay between effects due to statistical versus dynamical properties of the observed data. Temporal changes in the hemispheric predominance of the graph connectivity are found to lag those directly associated with the total hemispheric sunspot areas themselves.
We use visibility graphs to characterize asymmetries in the dynamics of sunspot areas in both...
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