Line-of-sight magnetic field and mean travel times of the average supergranule near disk center, as measured from HMI. The black circles are centered on the origin and have radii of 11 and 18 Mm. Left: absolute line-of-sight magnetic field B. The absolute value was taken after averaging B_LOS over 8 h. The colorbar is symmetrized around the spatial average (3.52 Gauss). Right: mean travel times for f modes (surface gravity waves). These travel times are the mean of outward and inward travel times measured between a central point and a surrounding annulus of radius 10 Mm and are sensitive to the magnetic field. The colorbar is symmetrized around zero (which is the mean value by construction).