Rotation of a Long-Lived Coronal Hole in Solar Cycle 24

Abstract

This paper discusses the results of a statistical study of the rotation characteristics of a long-livedgiant coronal hole. The study is based on observation data obtained by the Atmospheric Imaging Assemblyin the Fe XII 19.3 nm line aboard the Solar Dynamics Observatory spacecraft during the period from June2015 to March 2017; this was 24 Carrington revolutions. Four stages of the development of a coronal hole areconsidered separately: formation, two phases of a developed coronal hole, and the final phase. It has beenfound that the average rotation rate at a latitude of 40° is close to the standard speed at the beginning(12.75°/day) and in the first phase of maximum development (13°/day); it is lower in the second phase ofmaximum development (11.7°/day) and at the end of its existence (12.5°/day). A slight increase in velocity atthe final stage is associated with the restructuring of the coronal hole. According to modern theories, the rotationof the solar corona reflects the rotation of the subphotospheric layers. The higher layers of the coronareflect the rotation of the deeper layers of the Sun. The results obtained in our work show that the rotationrate of a giant coronal hole in the maximum phase of its development is greater than the rotation rate of thesolar disk. Perhaps this indicates that coronal holes can be associated with deep solar layers through the configurationof the global magnetic field and that the source of coronal hole formation is deeper than the sourceof the background field.