Solar global velocity oscillations and active region rotation

Abstract

Claverie et al.¹ have recently reported the detection of an approximately 13-day periodicity in measurements of the mean Doppler velocity shift of the integrated solar disk. They attribute this signal to the presence of a rapidly rotating core. Here we draw attention to the close correlation between this periodicity and the rotation of solar active regions across the disk. The presence of an active region should modulate the measured velocities due to the temperature sensitivity of the line measured. It seems likely that this is the origin of the signal observed by Claverie et al.