Solar Corona as Indicator of Differential Rotation of Subphotospheric Layers

Resumo

In our earlier work [2–4], we proposed using the coronal magnetic field as an implicit tracer when studying the properties of differential rotation of the solar corona. At present, this is virtually the only way to study the rotation of the Sun at large heliocentric distances up to the source surface. In the present work, calculations of the coronal magnetic field have been extended over a longer time interval, till December 31, 2015. It is shown that the solar corona rotates differentially at all heliocentric distances up to the source surface. The differential rotation gradient decreases with distance. As we approach the source surface, the corona rotation becomes more rigid, but even at large heliocentric distances it remains slightly differential. We believe that the differential rotation of the solar corona reflects the rotation of deep subphotospheric layers. In this case, the behavior of the coronal rotation characteristics can be used as indicator of differential rotation of the subphotospheric layers. We have compared the changes in the coronal rotation characteristics with distance with helioseismic data and obtained a satisfactory agreement. Cycle variations in the differential rotation of subphotospheric layers have been investigated for the first time.