Date : 01-03-2018
Time : 14:30:00
Speaker : Dr. Vincent Boening
Area : Udaipur Solar Observatory (USO)
Venue : USO Seminar Hall
The solar meridional flow is a crucial ingredient in modern dynamo theory. Seismic estimates of this flow have, however, been contradictory in deeper layers. Here, we develop and validate a method for computing spherical Born approximation kernels for time-distance helioseismology and we employ these kernels to invert for the deep solar meridional flow using 652 days of GONG data from 2004 - 2012. Above about 0.85 solar radii, our inversions confirm the result obtained by Jackiewicz et al. with the ray approximation regarding the general structure of the flow. This especially concerns a shallow return flow at about 0.9 solar radii, although some differences in flow magnitude are apparent. Below about 0.85 solar radii, we obtain several different results that are consistent with the measured travel times within the measurement errors. While one result is similar to the original single-cell flow found by Jackiewicz et al., the other results exhibit a multi-cell flow structure in the southern hemisphere. To reach an unambiguous conclusion on the meridional flow in this region, the errors in the measured travel times have to be considerably reduced. From this, I conclude that an unambiguous detection of the meridional flow is limited to a much shallower region than previously thought. This is a partial relief to the controversy about measurements of the deep solar meridional flow.