Statistical Analyses of Solar Active Region in SDO/HMI Magnetograms detected by Unsupervised Machine Learning Method DSARD

TL;DR

This paper introduces an unsupervised machine learning method called DSARD, based on DBSCAN, to automatically detect and analyze solar active regions in magnetograms, providing statistical insights across solar cycles 24 and 25.

Contribution

The paper develops and applies a novel unsupervised detection method for solar active regions, enabling large-scale statistical analysis and revealing Hale's law violations.

Findings

Most statistical results align with previous studies.

The method successfully identifies AR properties across solar cycles.

Detected Hale's law violations in 13-16% of ARs.

Abstract

Solar active regions (ARs) are the places hosting the majority of solar eruptions. Studying the evolution and morphological features of ARs is not only of great significance to the understanding of the physical mechanisms of solar eruptions, but also beneficial for the hazardous space weather forecast. An automated DBSCAN-based Solar Active Regions Detection (DSARD) method for solar ARs observed in magnetograms is developed in this work, which is based on an unsupervised machine learning algorithm called Density-Based Spatial Clustering of Applications with Noise (DBSCAN). The method is then employed to identify ARs on the magnetograms observed by the Helioseismic and Magnetic Imager (HMI) onboard Solar Dynamics Observatory (SDO) during solar cycle 24 and the rising phase of solar cycle 25. The distributions of the number, area, magnetic flux, and the tilt angle of bipolar of ARs in latitudes and time intervals during solar cycle 24, as well as the butterfly diagram and drift velocities are obtained. Most of these statistical results based on our method are in agreement with previous studies, which also guarantees the validity of the method. In particular, the dipole tilt angles in ARs in solar cycle 24 and the rising phase of solar cycle 25 are analyzed which reveal that 13% and 16% of ARs, respectively, violate Hale's law.