Nocturnal variation of rotational temperatures and band intensities at El Leoncito, during the night 22/23 Aug 2001. Besides slow variations due to the semidiurnal tide (in terms of O2 temperature, this is in fact the strongest tidal amplitude ever observed: 29 K ), a quite surprising feature is the very fast OH intensity increase around 3:50 LST. The intensity grows by more than a factor of two in only ten minutes. This is a "wall event", or "tidal bore", as confirmed by observations with the Boston University airglow imager (see Smith et al., 2006, in our list of papers).