Rotation of the large-scale solar magnetic fields in the equatorial region

A study is made of the rotation of large-scale magnetic fields using the synoptic maps from the Kitt Peak National Observatory for the time interval 1976-1985. The auto-correlation method and the mass-centers method of magnetic structures was applied to infer mean differential rotation profiles and rotation profiles separately for each magnetic field polarity. It has been found that in both hemispheres the leading polarity rotates faster than the following polarity at all latitudes by about 0.04 degrees day(-1). The maximum rotation rate of the leading polarity is reached at about 6 degrees latitude. In the mean profile for both polarities, this brings about two angular velocity maxima at 6 degrees latitudes in both hemispheres. Such a profile appears as to have a 'dimple' on the equator.