Imaging subsurface profiles of solar supergranules

      Supergranules are convectiveMrs flows with horizontal scales around ~30 Mm, observed all over the visible solar disk. The surface velocity of supergranules have been measured accurately with various techniques, however subsurface profiles of supergranules have proven difficult to measure. Helioseismology provides us with a window into the solar interior that might be used to image these flows, however previous attempts at a seismic inference have resulted in a range of possible models that seem to vary with the specific technique used in the analysis. This disparity in inferences calls for validation of the algorithms that are used to compute subsurface flow velocities. Recently Bhattacharya et al. (2016) carried out tests using synthetic travel times of seismic waves obtained by simulating wave propagation through a supergranule. Their technique demonstrated a potential to image sub-photospheric flows, but the inverted model failed to converge to the correct one. In this work we carry out a similar analysis, but using an alternate parametrization of the flow velocity in a basis of B-splines. This approach simplifies the inverse problem significantly, and we show that we are able to image the hitherto elusive subsurface vertical profiles of supergranules reasonably accurately. This might be a useful starting point for framing inversion algorithms to image supergranular flows in the Sun.