Composite masks showing the magnetic field with inclination less than 60° at τ_c = 0.95 (in the solar frame) in green and vertical field in the solar frame of less than − 100 G (opposite polarity field) in red. In the penumbra, the green color corresponds to the magnetic spines, and the black and red colors correspond to the intra-spines. The opposite polarity field in the penumbra is mostly found adjacent to the spines. Opposite polarity field is found also near some strong flux concentrations (plage and pores), and in a few cases near network field. Areas with field strength smaller than 350 G are shown black. The FOV is 35   ×   35′′ and corresponds to that shown in Figs. 4 and 6. Tick marks are at 1′′ intervals.