Complex Network for Solar Active Regions

TL;DR

This study constructs a complex network of solar active regions to analyze their properties, revealing self-organized criticality, scale-free, and small-world characteristics, and linking network hubs to flare occurrence probabilities.

Contribution

The paper introduces a novel complex network model of solar active regions, demonstrating their scale-free and small-world properties and their relation to solar flare activity.

Findings

ARs network exhibits scale-free and small-world properties.

ARs system shows self-organized criticality.

Flares are more likely at network hubs.

Abstract

Here, we developed a complex network of solar active regions (ARs) to study various local and global properties of the network. The values of the Hurst exponent ($0.8-0.9$) were evaluated by both the detrended fluctuation analysis and the rescaled range analysis applied on the time series of the AR numbers. The findings suggest that ARs can be considered as a system of self-organized criticality. We constructed a growing network based on locations, occurrence times, and the lifetimes of 4,227 ARs recorded from 1 January 1999 to 14 April 2017. The behaviour of the clustering coefficient shows that the ARs network is not a random network. The logarithmic behaviour of the length scale has the characteristics of a so-called \textquotedblleft small-world network\textquotedblright. It is found that the probability distribution of the node degrees for undirected networks follows the power-law with exponents of about 3.7 to 4.2. This indicates the scale-free nature of the ARs network. The scale-free and small-world properties of the ARs network confirm that the system of ARs forms a system of self-organized criticality. Our results show that the occurrence probability of flares (classified by GOES class C $> 5$, M, and X flares) in the position of the ARs network hubs take values greater than that obtained for other nodes.