Large-scale horizontal flows in the solar photosphere. II. Long-term behaviour and magnetic activity response
2008
Abstract
We apply the recently developed method utilised to measure the photospheric flow fields to the series of MDI Dopplergrams covering almost one solar cycle to generate the information about the long-term behaviour of surface flows. Our method clearly reproduces the widely accepted properties of mean flow field components, such as torsional oscillations and a pattern of meridional circulation.
The relation between the magnetic activity and the mean zonal motion is studied. We found evidence that the emergence of compact magnetic regions locally accelerates the rotation of the supergranular pattern in their vicinity and that the presence of magnetic fields generally decelerates the rotation in the equatorial region.