Coronal Hole and Solar Global Magnetic Field Evolution in 1976-2012

TL;DR

This study analyzes the evolution of coronal holes and the solar global magnetic field from 1976 to 2012, revealing regularities and wave patterns that reflect magnetic cycle transitions and polar field reversals.

Contribution

It provides a detailed analysis of coronal hole distributions and their relation to magnetic field cycles, including the discovery of two types of non-polar coronal hole waves over multiple solar cycles.

Findings

Coronal hole distributions match global magnetic cycle evolution.

Two types of non-polar coronal hole waves identified.

Coronal hole waves have a period of approximately 22 years.

Abstract

Coronal hole spatial-temporal evolution is studied and comparison made with that of the solar global magnetic field in cycles 21-23 (1976-2012). The latitude-longitude distribution dynamics of coronal holes and the regularities in the global magnetic field associated with the solar polar field reversal are analyzed. Polar and non-polar coronal hole populations are considered. The investigation reveals some temporal and spatial regularities in coronal hole distributions that match well the global magnetic-field cycle evolution. The results show that the non-polar coronal hole longitudinal distribution follows all configuration changes in the global magnetic-field structure. Reorganizations of the global magnetic-field and coronal hole distributions occur simultaneously during a time interval of a few solar rotations. The cycle evolution of the non-polar coronal holes reflects the transition of the solar global magnetic field from the zonal structure to sectorial andvice versa. Two different type waves of non-polar coronal holes are revealed from their latitudinal distribution. The first one is short poleward waves. They trace the poleward motion of the unipolar photospheric magnetic fields from approximately 35 deg to the associated pole in each hemisphere and the redevelopment of a new-polarity polar CH. Although they start the poleward movement before the change of the polar magnetic field in the associated hemisphere, they reach the pole after the polar reversal. The other type of non-polar CH wave forms two sinusoidal branches associated with the positive- and negative-polarity magnetic fields. The complete period of the wave was equal to approximately 268 CRs (22 years). These wave CHs arrive at high latitudes during declining phases when the new polarity polar CHs are already completely formed.