Temporal variations of solar rotation during solar cycle 23

With 11 years of helioseismic data now available, we study the temporal variation in rotation rate in the solar interior. In addition to the well known zonal flow pattern, we also find that at low latitudes the pattern is shifting upwards with time and that the pattern extends almost to the base of the convection zone. By fitting a periodic function to the pattern it is possible to extract the temporal variation at each latitude and depth. This pattern can be compared with predictions of solar dynamo theories. We also examine possible periodic variations in the rotation rate in the tachocline region