Differential rotation of the solar corona and its importance for helioseismology

It is shown that the solar corona rotates differentially at all heliocentric distances up to the source surface. As the distance increases, the differential rotation gradient decreases, and the rotation becomes more and more rigid. At small distances, the corona at latitudes above $\approx \pm 40^{\circ}$ rotates faster than the photosphere at the same latitudes. The type of the rotation depends also on the phase of the activity cycle. The differential rotation gradient is the largest in the vicinity of the cycle minimum. It is shown that time variations in the coronal rotation characteristics are associated with the tilt of the magnetic equator of the Sun. Based on the concept that the differential rotation of the corona reflects the rotation of deep subphotospheric layers, we compared the changes in the coronal rotation characteristics with distance with the helioseismic data and showed their satisfactory agreement. The results obtained allow us to suggest that the rotation of the solar corona can be used as indicator of the differential rotation of subphotospheric layers and calculate the nature of some current sheets in heliosphere/