Left: magnetic field B_network around the average supergranule near disk center as a function of azimuthal angle ψ. To obtain B_network, the magnetic field B was averaged over segments (width 10° in ψ) of a concentric ring around the center of the average supergranule. The inner and outer limits of the ring are 11 and 18 Mm (circles in Fig. 2). The thin blue lines give the 1σ bounds. The dashed line is a least-squares fit to a cosine of the form specified by Eq. (1). The maximum of the cosine is fixed at ψ = 0° (west direction). For comparison, the horizontal black line shows the background field Gauss. Right: as for the left, but for f-mode mean travel times. In addition to the result at disk center, the mean travel times at other positions along the equator are shown (using patches centered at longitudes ± 20°, ± 40°, and ± 60° away from the central meridian, averaged over east and west). The dashed line represents the cosine function given by Eq. (2). By construction, the mean travel time in the background is zero.