Dynamics of magnetic tubes during the formation of a large sunspot

The emergence of new magnetic flux in the powerful active region NOAA 10488 on the Sun and the formation of a leading spot is studied using SOHO/MDI data. Magnetograms of the longitudinal magnetic field and radial-velocity data obtained with a temporal resolution of 1 min are analyzed. The analysis begins several hours before the appearance of the top of a rising buoyant loop-like tube of magnetic field in the photosphere and finishes two days later, when the leading spot has formed. The emerging arches of magnetic field had a complex, multi-layered structure. Their apparent concentration can be explained by the emergence of the leading base of an ascending ?? tube. The new magnetic flux emerged in the inner parts of the active region throughout the formation of the leading sunspot, and was accompanied by the development of a penumbra and the appearance of the Evershed effect in the southwest sector of the sunspot. Simultaneous with the development of Evershed flows, the outer parts of the longitudinal magnetic field were gradually separated from the sunspot in the radial direction. As a result, a moat and a quasi-annular structure were formed in the magnetic field. The formation of a ??moat?? cell is part of the unified large-scale formation of the sunspot and the entire active region. The formation of an active region and of its structures is a manifestation of large-scale processes taking place in subphotospheric layers.