Example of the velocity variation in different rings of the penumbra, together with the results of the fit. Red: Fe i 5198.71 Å line (dashed line for the fit), black: Fe ii 5197.58 Å line (solid line for the fit). Horizontal dashed and solid lines give the average velocity values. Velocities are λ-meter velocities corresponding to the position close to the line core for both lines, λ₁. We note that the velocities from the Fe i and Fe ii lines correspond to different heights.