Poster abstract details

While sunspots are easily observed at the surface, determining their sub-surface structure is not at all trivial. There are two main hypotheses for the structure of the sub-surface magnetic configuration of the spot: the monolithic model and the cluster model. However, current linear inversion techniques do not yet allow helioseismology to probe the internal structure of the sunspot with sufficient confidence to distinguish between monolith and cluster models. Furthermore, interpretations of data have been somewhat ambiguous and inconsistent for applications of local helioseismic methods in solar active regions. But thanks largely to two recent HELAS Local Helioseismology Workshops on this topic, significant progress has been made in addressing some of the outstanding issues in sunspot seismology. Extensive analyses of the sunspot in NOAA 9787 were undertaken at these workshops, using a variety of different helioseismic diagnostic methods and numerical simulations, revealing some very interesting (and sometimes controversial) results, leading to a new paradigm in sunspot seismology. We shall summarize these findings here. In particular, we find that the sunspot introduces a shallow positive wave-speed perturbation (unlike the traditional two-layer model), while both f- and p-mode travel times are now found to be consistent with a horizontal outflow in the sunspot's moat.