Active Longitudes Revealed by Large-scale and Long-lived Coronal Streamers

TL;DR

This study uses ultraviolet images to identify persistent, long-lived coronal streamers and sunspot clusters, revealing non-uniform active longitudes on the Sun that rotate faster than the surface and are linked to underlying azimuthal structures.

Contribution

It provides observational evidence of long-lived active longitudes and associated sunspot clusters, highlighting their non-uniform distribution and faster rotation rates.

Findings

Four main sunspot clusters occupy two ~100° zones separated by 180°.

Sunspot clusters rotate ~5% faster than the surface and convection zone.

Over 75% of sunspots are concentrated in these clusters during 2006-2011.

Abstract

We use time-series ultraviolet full sun images to construct limb-synoptic maps of the Sun. On these maps, large-scale, long-lived coronal streamers appear as repetitive sinusoid-like arcs projected over the polar regions. They are caused by high altitude plasma produced from sunspot-rich regions at latitudes generally far from the poles. The non-uniform longitudinal distribution of these reveals four longitudinal zones at the surface of the sun from which sunspots erupt preferentially over the 5-year observing interval (2006 January to 2011 April). Spots in these zones (or "clusters") have individual lifetimes short compared to the lifetimes of the coronal features which they sustain, and erupt at different times. The four sunspot clusters contain >75% of all numbered sunspots in this period. They occupy two distinct longitudinal zones separated by ~180 degree and each spanning ~100 degree in longitude. The rotation rates of the spot clusters are ~5% faster than the rates at both the surface and the bottom of the convection zone. While no convincing theoretical framework exists to interpret the sunspot clusters in the longitude-time space, their persistent and nonuniform distribution indicates long-lived, azimuthal structures beneath the surface, and are compatible with the existence of previously-reported active longitudes on the sun.