Hemispheric analysis of the magnetic flux in regular and irregular solar active regions

TL;DR

This study analyzes the hemispheric distribution and magnetic morphology of solar active regions over multiple solar cycles, revealing complex cyclic variations, hemispheric imbalances, and potential dynamo process insights.

Contribution

It introduces a detailed hemispheric analysis of active regions based on magneto-morphological classification, highlighting differences between regular and irregular ARs and their implications for solar dynamo models.

Findings

Irregular ARs show pronounced peaks near polar field reversal.

Hemispheric imbalance in irregular ARs suggests weakening of toroidal field.

Signs of ~15-year oscillations in quadrupolar flux component.

Abstract

Studying the hemispheric distribution of active regions (ARs) with different magnetic morphology may clarify the features of the dynamo process that is hidden under the photospheric level. The magnetic flux data for 3047 ARs from the CrAO catalog between May 1996 and December 2021 (cycles 23 and 24) were used to study ARs cyclic variations and perform correlation analysis. According to the magneto-morphological classification (MMC) of ARs proposed earlier, subsets of the regular (obeying empirical rules for sunspots) and irregular (violating these rules) ARs were considered separately. Our analysis shows the following. For ARs of each MMC type, in each of the hemispheres, time profiles demonstrate a multi-peak structure. The double-peak structure of a cycle is formed by ARs of both MMC types in both hemispheres. For the irregular ARs, the pronounced peaks occur in the second maxima (close to the polar field reversal). Their significant hemispheric imbalance might be caused by a weakening of the toroidal field in one of the hemispheres due to the interaction between the dipolar and quadrupolar components of the global field, which facilitates the manifestation of the turbulent component of the dynamo. The similarity of the irregular ARs activity that was found in adjacent cycles in different hemispheres also hints at realization of the mix-parity dynamo solution. For the quadrupolar-like component of the flux (compiled in the simple axisymmetric approximation), signs of oscillations with a period of about 15 years are found, and they are pronounced specifically for the irregular groups. This MMC type ARs might also contribute in $\alpha$-quenching.