The rotation of the solar corona differs from that of the photosphere and chromosphere for the following two reasons: the solar corona rotates rigidly over a wide latitude zone in the minimum phase of the solar cycle, and the degree of differential rotation of the solar corona depends on the solar cycle (Antonucci and Svalgaard, 1974). Part of this behavior was confirmed by Skylab with the observation of the rotation of coronal holes.
A recent study (Antonucci, Hoeksema and Scherrer, 1990) on the photospheric magnetic field, observed at the Wilcox Solar Observatory over an entire solar cycle, indicates that the dipolar and quadrupolar components of the field also show rigid rotation over wide latitude zones and a dependence on the solar cycle. This clearly indicates that the coronal features mainly contributing to rigid rotation are coupled with the magnetic dipole and quadrupole of the sun
An unexpected strong asymmetry in the rotation of the north and south hemispheres was found with the study of the photospheric magnetic field. This indicates a weak coupling between the magnetic fields of the two hemispheres. If the interpretation of the link between magnetic and coronal rotation is correct, we should also find a latitudinal asymmetry in the rotation of the extended corona, which is more influenced than the inner corona by the magnetic dipole and quadrupole of the sun.
It is to be noted that, independent of the above specific interests
concerning the influence of
the magnetic fields on the extended corona and the rotation of the solar
dipole and quadrupole, there is not yet a complete and
continuous determination of solar rotation as a function of height up to
5 
(possibly 10 
).
The measurement of the rotation of the extended corona can be easily
achieved by using regular synoptic observations of the extended corona in
Ly
and O VI. Therefore no specific UVCS observing mode is required.
Rotation of the Extended Solar Corona
