Abstract

We apply the helioseismic methodology of Legendre Function Decomposition to 7.5 years of Dopplergrams obtained by the Helioseismic and Magnetic Imager (HMI) as the basis of inferring the depth variation of the meridional flow between 20∘ and 60∘ latitude in both hemispheres. We assess and remove ... Show moreWe apply the helioseismic methodology of Legendre Function Decomposition to 7.5 years of Dopplergrams obtained by the Helioseismic and Magnetic Imager (HMI) as the basis of inferring the depth variation of the meridional flow between 20∘ and 60∘ latitude in both hemispheres. We assess and remove center-to-limb artifacts using measurements obtained by applying the procedure to pseudo poles at the east and west limbs. Forward modeling is carried out to evaluate the consistency of the corrected frequency shifts with models of the depth variation of the meridional circulation in the top half of the convection zone. The observations are consistent with a return flow in the northern hemisphere below about 40 Mm depth, but no obvious return flow in the south. Show less