Abstract | Predicting the emergence and evolution of solar active regions is one of the very important problems in solar physics. Local helioseismology
provides a tool for studying this problem. However, previous studies showed that the rapid emergence of magnetic flux poses significant constraints on an unambiguous detection of subsurface pre-emergence
structures. Detecting those structures and other pre-emergence signatures, before the first magnetic field elements appear on the surface, would improve our understanding of solar magnetism and benefit space weather forecasting. We investigate this problem by applying deep-focus time-distance measurements on MDI and new HMI helioseismic observations. We show the results of our study and discuss potential detection of pre-emergence signatures. |