  Rotation of the leading sunspot of active region NOAA 10421 was investigated
using magnetograms and Dopplergrams from the MDI instrument of the Solar and
Heliospheric Observatory (SOHO), and white-light images from the Transition
Region and Coronal Explorer (TRACE). The vertical, radial, and azimuthal
axisymmetrical components of both magnetic and velocity field vectors were
reconstructed for the sunspot umbra and penumbra. All three components of both
vectors in the umbra and penumbra show torsional oscillations with the same
rotational period of about 3.8 days. The TRACE white-light data also show that
the sunspot umbra and penumbra are torsionally rotating with the same period.
Possible mechanisms of sunspot torsional motions are discussed.
