Observations of discrete arcs with the Viking Ultraviolet Imager.

The Viking satellite launched in February, 1986 carried UV Imager (UVI), that acquired global images of the aurora in one-second exposures that could be telemetered to the ground in 20 to 80 s. The auroral arc is a widely used term that is applied to features occurring in different parts of the auroral oval. Here, a brief survey of the types of arc structures seen by the UVI in different parts of the oval is presented. This raises the question as to whether compatible classifications between the satellite images and the higher resolution ground-based images can be reached. In the long term, the satellite images should provide a more useful classification scheme for these features.