Leading spot of NOAA 11024 observed on July 4, 2009, 08:37 UT through the Ca ii K filter with FWHM 1 nm. Rectangle “1”: part of the light bridge where shear motions are found; the inset ‘1’ shows this LB area rotated to the horizontal and expanded by a factor of two. The vertical white bars in the inset represent the spatial extension selected to create the space-time slices shown in Fig. 2; rectangle “2”: part of umbra where umbral dots (UDs) were tracked; rectangle “3” (only corners marked): upper umbral border for space-time slices of the line-of-sight component of the magnetic field, B_LOS. The latter also from 08:37 UT is shown in the inset “3” (dark meaning the main polarity of the sunspot B_LOS).