THE MAGNETIC-FIELDS OF ACTIVE REGIONS .4. MERIDIONAL MOTIONS

Daily magnetogram data are analyzed to examine the meridional component of motions of active regions defined by magnetic fields measured with the Mount Wilson magnetograph. The period covered by this daily data set is 1967 through April 9, 1990. Meridional motions of all the active regions observed in this interval show a different latitude dependence than is shown by most other solar surface tracers: the higher the latitude, the greater is the relative equatorward drift velocity. However, the subsets of the data containing no increase or decrease of region size or showing decrease in size only lead to no latitude dependence of meridional motion, which implies that there is a very large effect due to the growth of regions. In this study only regions showing no growth or decay were used in the analysis. There is only a very slight variation of latitude dependence of meridional motions with cycle phase. At the decline from maximum there is a weak relationship found, at other phases there is no correlation. Meridional motions are correlated with rotation rate residual velocities. Slower rotation rates are found for poleward moving regions, and faster rotation rates are found for equatorward moving regions - a result similar to that for sunspots. Covariances of these quantities are comparable in magnitude to those found for sunspot groups.