Examples of measured quantities with superimposed contours outlining the six radial zones in the penumbra, numbered 1 (adjacent to the umbra) to 6 (the outermost penumbra). Radial zones 2–4 constitute what is referred to as the “interior penumbra”. In the top row are shown (left to right) the 538 nm continuum intensity, the COG velocity in the same line and the LOS component of the magnetic field, obtained with the COG method. In the lower row are shown the same quantities but high-pass spatially filtered to remove large-scale azimuthal and radial variations. Tick marks are at 1′′ intervals. The arrow points in the direction of Sun center.