Portion of the (center-side) penumbra of the main sunspot in AR 10930 (cf. Fig. 5 in Siu-Tapia et al. (2017)). Panel a: map of the magnetic field strength at log(τ) = 0, as inferred with SPINOR 2D inversions. The arrow points towards the solar-disk center. Panel b: line-of-sight velocity as inferred with SPINOR 2D inversions at log(τ) = 0. Positive values (red-to-yellow colors) indicate plasma motions away from the observer, while negative values (blue colors) indicate motions towards the observer. Solid and dashed black contour lines were placed at I_c/I_QS = 0.26 and I_c/I_QS = 0.94, respectively. The large penumbral sector where red-to-yellow colors dominate harbors a fast counter-EF which supersonically sinks (with speeds larger than 12 km s⁻¹) near the inner penumbral boundary (Siu-Tapia et al. 2017). The color-bar scales have been saturated.