Presentation #502.01 in the session Solar Interior Flow and Dynamics.
The solar tachocline is almost coincident with the base of the convection zone, however, it is known to be prolate. The shape of the convection-zone base, on the other hand, is generally assumed to be spherically symmetric. Early investigations failed to find any statistically significant signs of asphericity, but the helioseismic data sets used in those investigations were obtained from relatively short time series, ranging from 72 days to 1 year. We now have more than 2 decades of helioseismic observations, which allows us to obtain more precise mode frequencies and splittings using much longer time series. We report results of a new investigation into the shape of the solar convection zone using data from GONG, MDI and HMI and show evidence that the solar convection zone base is likely to have a small asphericity.