  Torsional oscillations represent bands of fast and slow zonal flows around
the Sun, which extend deep into the convection zone and migrate during solar
cycles towards the equator following the sunspot butterfly diagram. Analysis of
helioseismology data obtained in 1996-2018 for almost two solar cycles reveals
zones of deceleration of the torsional oscillations inside the Sun due to
dynamo-generated magnetic field. The zonal deceleration originates near the
bottom of the convection zone at high latitudes, and migrates to the surface
revealing patterns of magnetic dynamo waves predicted by the Parker's dynamo
theory. The analysis reveals that the primary seat of the solar dynamo is
located in a high-latitude zone of the tachocline. It suggests a dynamo
scenario that can explain 'extended solar cycles' previously observed in the
evolving shape of the solar corona. The results show a substantial decrease of
the zonal acceleration in the current solar cycle and indicate further decline
of activity in the next solar cycle. Although the relationship between the
magnitude of zonal deceleration and the amount of emerged toroidal field that
leads to formation of sunspots is not yet established, the results open a new
perspective for solar cycle modeling and prediction using helioseismology data.
