Azimuthal averages of B (upper panel) and γ (lower panel) along the sunspot radius at three optical depths. Also shown are rms variations for the uppermost and lowermost node positions (blue and red error bars, respectively). The two vertical dashed lines represent the inner and outer boundaries of the sunspot penumbra (on average). The two dotted lines outline the radius between which a positive field gradient is seen (i.e., field strength increasing upward).