All-sky imaging observations of mesospheric fronts in OI 557.7 nm and broadband OH airglow emissions: Analysis of frontal structure, atmospheric background conditions, and potential sourcing mechanisms

All-sky imaging observations of distinct, large horizontal transient mesospheric structures with a spatial scale of ∼100 km detected in images of broadband OH and OI 557.7 nm airglow emissions were made over Clemson, South Carolina, on the night of 14-15 October 2001. We designate these structures as mesospheric fronts and present a detailed summary of this night series of observations, paying particular attention to the details of the different frontal structures, the wave-like activity seen throughout the night, and the background atmospheric conditions. These data are compared to other observations of similar mesospheric fronts found in the literature, and we seek to understand them in relation to mesospheric bores, ducted gravity waves, mesospheric wall events, and nonlinear gravity wave interactions. We find that the observed frontal characteristics and the atmospheric background structure exhibit a close resemblance to previous observations of mesospheric bores. Owing to this similarity, and supported by gravity wave ray-tracing experiments, we propose a sequence of events that generated the mesospheric fronts observed in the airglow emission. Furthermore, we note this similarity in atmospheric structure suggests a potential means of predicting the occurrence of such mesospheric phenomena.