Migrating zonal flows in the solar convection zone

With nine years of combined observations from the Michelson Doppler Imager (MDI) and Global Oscillation Network Group (GONG) projects, the pattern of migrating zonal flows in the convection zone can be seen in more detail than ever before. To make the above plot, the rotation-rate residuals after subtraction of a temporal mean from RLS inversions were fitted with 11-year and 11/3-year sinusoids (after Vorontsov et al. 2002), and the fits extrapolated to complete the solar cycle. This combination gives a more stable prediction than other possible choices such as 11/2 years for the second period. The flows can be seen to penetrate deep within the convection zone, and we can begin to make inferences about the possible depth variation of the phase of the flow pattern. The branch that will be associated with the next solar cycle can be seen emerging in the 2003 data. See the June 2004 NOAO Newsletter (currently only available in PDF format).