Probing Supergranular Flow in the Solar Interior

Abstract

Helioseismic correlation data computed from SOHO MDI high-resolution Doppler images were inverted for solar subsurface supergranular flow, using an improved forward model. The statistical error of the inversion is set by the stochastic nature of solar wave excitation, which limits the detection of supergranular flow with these data to the first 4 or 5 Mm below the photosphere. The photospheric supergranulation pattern, averaged over the ~34 hour duration of the data set, is found to persist over the detectable depth range. Contrary to some recent findings, there is no indication of a flow reversal at a depth between 5 and 6 Mm. However, since the depth of the putative reversal is at the edge of the detectable range for these data, the discrepancy is probably not significant.