Decay of Activity Complexes, Formation of Unipolar Magnetic Regions and Coronal Holes in their Causal Relation

TL;DR

This study investigates how the decay of solar activity complexes influences the formation of unipolar magnetic regions and coronal holes, revealing their causal relationships and impact on the Sun's magnetic flux during the 2014 cycle.

Contribution

It provides a detailed analysis of the causal links between activity complex decay, magnetic field evolution, and coronal hole formation using multi-instrument solar observations.

Findings

Coronal holes form from ensembles associated with decaying activity complexes.

The south polar coronal hole originated from multiple activity complexes in 2014.

Large-scale magnetic field rearrangements are driven by activity complex decay.

Abstract

North-south asymmetry of sunspot activity resulted in an asynchronous reversal of the Sun's polar fields in the current cycle. The asymmetry is also observed in the formation of polar coronal holes. A stable coronal hole was first formed at the South Pole, despite the later polar-field reversal there. The aim of this study is to understand processes making this situation possible. Synoptic magnetic maps from the Global Oscillation Network Group and corresponding coronal-hole maps from the Extreme ultraviolet Imaging Telescope aboard the Solar and Heliospheric Observatory and the Atmospheric Imaging Assembly aboard the Solar Dynamics Observatory are analyzed here to study a causal relationship between the decay of activity complexes, evolution of large-scale magnetic fields, and formation of coronal holes. Ensembles of coronal holes associated with decaying active regions and activity complexes are presented. These ensembles take part in global rearrangements of the Sun's open magnetic flux. In particular, the south polar coronal hole was formed from an ensemble of coronal holes that originated after the decay of multiple activity complexes observed during 2014.