Evidence for the return meridional flow in the convection zone from latitude motions of sunspots

Abstract

AbstractWe have derived the latitude motions of sunspots classified into three area categories using the measures of positions and areas of their umbrae from the white – light images of the Sun for the period 1906 – 1987 from the Kodaikanal Observatory archives. The latitude motions are directed equator – ward in all the three area classes. We interpret that these equator – ward latitude motions reflect the meridional flows at the three depths in the convection zone where the magnetic flux loops of the spots of the three area classes are anchored. We obtain estimates of the anchor depths through a comparison of the rotation rates of the spots in each area class with the rotation rate profiles from helioseismic inversions. The equator – ward flows measured by us thus provide evidence of the return meridional flows in the convection zone as required in the flux transport solar dynamo models. We have done an identical analysis using a similar data set derived from the photoheliogram collections of the Mt.Wilson Observatory for the period 1917 – 1985. There is good agreement between the results from the data sets of the two observatories.