Latitudinal distribution of travel times in the upper solar convection zone

Abstract

We applied the time-distance technique to GONG+ data in 2001 (at solar maximum) and 2006 (at solar minimum) to study the influence of surface activity on the latitudinal distribution of travel times of acoustic waves in the upper solar convection zone. We find that surface activity is the dominant source of travel time differences over the solar cycle. Removal of the surface activity with a masking method reveals a residual travel-time shift of 0.5 sec, corresponding to a surface temperature change of 0.25° K over the solar cycle.