We estimate the temporal change of magnetic flux perpendicular to the solarsurface in a decaying active region by using a time series of the spatialdistribution of vector magnetic fields in the photosphere. The vector magneticfields are derived from full spectropolarimetric measurements with the SolarOptical Telescope aboard Hinode. We compare a magnetic flux loss rate to a fluxtransport rate in a decaying sunspot and its surrounding moat region. Theamount of magnetic flux that decreases in the sunspot and moat region is verysimilar to magnetic flux transported to the outer boundary of the moat region.The flux loss rates [$(dF/dt)_{loss}$] of magnetic elements with positive andnegative polarities are balanced each other around the outer boundary of themoat region. These results suggest that most of the magnetic flux in thesunspot is transported to the outer boundary of the moat region as movingmagnetic features, and then removed from the photosphere by flux cancellationaround the outer boundary of the moat region.
展开▼
