What type of propagation allows signals to be heard in the transmitting station’s skip zone?

When transmitting via skywave, the radio signal goes up to the ionosphere and bounces back down some distance away, jumping completely over the intermediate area known as the skip zone. Scatter propagation occurs when irregularities in the ionosphere cause a small portion of the radio wave to diffuse in multiple directions rather than bouncing cleanly. Some of this diffused energy is directed straight down or backward into the skip zone. This allows a receiving station located in the normally "dead" skip zone to hear the transmission, albeit weakly and with distortion. Options like Faraday rotation (which affects polarization) or chordal hop (which involves multiple ionospheric bounces without hitting the ground) do not fill in the skip zone.