Abstract:
A key component of solar interior dynamics is the meridional circulation
(MC), whose poleward component in the surface layers has been well observed.
Time-distance helioseismic studies of the deep structure of MC, however, have
yielded conflicting inferences. Here, following a summary of existing results we
show how a large center-to-limb systematics (CLS) in the measured travel times of
acoustic waves affect the inferences through an analysis of frequency dependence of
CLS, using data from the Helioseismic and Doppler Imager (HMI) onboard Solar
Dynamics Observatory (SDO). Our results point to the residual systematics in travel
times as a major cause of differing inferences on the deep structure of MC.
