An unusual airglow wave event observed at Cachoeira Paulista 23° S Original Research Article

An all-sky CCD airglow imager has been used to obtain a wealth of data on the MLT airglow emissions from Cachoeira Paulista, Brazil (22.7° S, 45.0° W). Measurements of the NIR OH, OI(557.7 nm), O2(0,1) and the thermospheric OI(630.0 nm) emissions have been made since October 1998. In addition, simultaneous measurements of the airglow zenith intensities and rotational temperatures, and vertical wind structure between 80 and 100 km were made using a co-located multi-channel photometer and a meteor radar. On the night of July 13, 1999, the CCD images showed active wave events exhibiting a variety of short period wave structures. The activity started with ripple patterns over the whole sky, lasting for almost one hour. Later the patterns changed to extensive band-like structures that lasted for several hours. After local midnight a bore-like wave-front passed overhead propagating towards the North. When the front was in the zenith the image data showed an increase in both the OI (5577 nm) and O2 (0,1) emissions, whilst a decrease in the OH intensity was observed, which is opposite to that observed by Taylor, (1995a). The co-located photometer revealed an exceptionally large intensity (40%) and temperature (∼12%) perturbation throughout the night that appears to be associated with a large-scale gravity wave perturbation with significant vertical phase shift between the different emissions.