This is the first report of the most comprehensive 630.0 nm airglow limb images taken using Imager of Sprites and Upper Atmospheric Lightnings (ISUAL) onboard FORMOSAT-2. The limb scans reveal two distinct airglow layers: the upper one corresponds to the thermospheric O(D-1) emission and the lower one corresponds to the OH (9-3) emissions. Sequences of such observations are combined to generate altitude-latitude maps of the emissions, which reveal intensity enhancements of both the layers at certain locations where they often appear to be linked/joined vertically. A detailed analysis of the location and occurrence of the enhancements in the entire observations, together with simulations of the emissions suiting the ISUAL limb geometry are carried out to understand the causes and related processes.
