Rotation of the magnetic elements in polar regions on the Sun

Using the Michelson Doppler Imager (MDI) data from Solar and Heliospheric Observatory (SOHO), the rotation rate of the unipolar magnetic regions in North high-latitude regions of the Sun is estimated by tracking individual magnetic elements. The analysis reveals a strong spin down near the pole, which is greater than the Doppler and magnetic rotation rates estimated by Snodgrass & Ulrich (1990), and rotation rate inferred from helioseismology (Birch & Kosovichev 1998), and is probably related to variation of velocity gradient in the subsurface shear layer. (© 2007 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim)