Three scenarios for shaping 'ears' in planetary nebulae

We present three scenarios for shaping planetary nebulae (PNe) with ears : (i) Ejection of early and shortduration jets into a spherical wind. (ii) Fast wind ejection into a slow dense wind and then jet ejection into the hot bubble. (iii) Interaction of fast wind with two opposite punctured regions. We find that all three scenarios can lead to the formation of ears. Ears are two opposite polar protrusions from the main nebula that are smaller than the main nebula and with a cross section that decreases monotonically from the base of each ear at the shell to its far end. Ears are generally indicative of the operation of jets, but in a rich spectrum of flow structures, jet properties and time and duration of activity.