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

Abstract

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.

Visibility Graphs for Image Processing

“…Theoretical research on visibility graphs has elaborated on mathematical methods [8][9][10][11] and some rigorous results on the properties of these graphs when associated to canonical models of complex dynamics have been obtained [12][13][14][15]. From a practical point of view, this method has been used as a feature extraction procedure to construct feature vectors from time series for statistical learning purposes (see [16][17][18][19][20][21][22] for just a few examples in the life sciences or [23][24][25][26][27][28][29][30] for other applications in the physical sciences). Very recently [31], this paradigm has been theoretically extended to handle scalar fields.…”

Stability of exoplanetary systems retrieved from scalar time series

“…However, other types of networks are suitable to explore the dynamical variability. Visibility graphs (Lacasa et al 2008;Zou et al 2014;Mutua et al 2016) are promising candidates to use them as an alternative approach in planetary dynamics.…”

Multiplex multivariate recurrence network from multi-channel signals for revealing oil-water spatial flow behavior

“…Complex network theory [8][9][10][11][12][13][14][15][16][17][18] has undergone an explosive growth in recent years. In particular, complex network analysis of time series 19 has been well developed and it contributes greatly to solve challenging problems in different research fields.…”