Advances in Time-Distance Helioseismology

Tom Duvall (GSFC)

Time-distance helioseismology, in which travel times between photospheric locations are measured for waves that traverse the solar interior, continues to be an important technique in the helioseismology toolbox. Recently the technique has been extended to studies of small features (magnetic elements) and small, short-lived features (granulation). Although the amount of information that can be extracted from these subwavelength features is somewhat limited, we really have no other subsurface observations of granulation to compare with detailed simulations. In this talk, these recent extensions of time-distance helioseismology will be discussed as will selected results of time-distance studies of supergranulation, active regions, solar rotation, meridional circulation, far-side measurements, and a possible detection of the magnetic field at the bottom of the convection zone.