Magnetic fluxes of solar active regions of different magneto-morphological classes: I. Cyclic variations

TL;DR

This study analyzes magnetic flux variations in 3046 solar active regions over 25 years, revealing how different classes of active regions follow the solar cycle and contribute to solar magnetic activity.

Contribution

It provides a comprehensive analysis of magnetic flux evolution across various active region classes and links their behavior to the solar dynamo process.

Findings

Magnetic fluxes from different AR classes evolve synchronously with the solar cycle.

Deepest solar minimum features only simple ARs (A1 and B1).

Complex ARs shape the fine structure of solar maximum.

Abstract

Data for 3046 solar active regions (ARs) observed since May 12, 1996 to December 27, 2021 were utilized to explore how the magnetic fluxes from ARs of different complexity follow the solar cycle. Magnetograms from the Michelson Doppler Imager instrument on the Solar and Heliospheric Observatory and from the Helioseismic and Magnetic Imager instrument on the Solar Dynamics Observatory were utilized. Each AR was classified as a regular bipolar AR (classes A1 or A2), or as an irregular bipolar AR (class B1), or as a multipolar AR (classes B2 or B3). Unipolar ARs were segregated into a specific class U. We found the following results. Unsigned magnetic fluxes from ARs of different classes evolve synchronously following the cycle, the correlation coefficient between the flux curves varies in a range of (0.70 - 0.99). The deepest solar minimum is observed simultaneously for all classes. Only the most simple ARs were observed during a deepest minimum: A1- and B1-class ARs. The overall shape of a cycle is governed by the regular ARs, whereas the fine structure of a solar maximum is determined by the most complex irregular ARs. Approximately equal amount of flux (45$-$50% of the total flux) is contributed by the A-class and B-class ARs during a solar maximum. Thus, observations allow us to conclude that the appearance of ARs with the magnetic flux above 10$^{21}$ Mx is caused by the solar dynamo that operates as a unique process displaying the properties of a non-linear dynamical dissipative system with a cyclic behaviour and unavoidable fluctuations.