Optical observations of gravity waves in the auroral zone

Abstract

Night-time observations of O( 1D) λ630 nm and O( 1S) λ558 nm thermospheric emissions were made at Mawson, Antarctica (67.6°S, 62.9°E) from 1982 to 1989, using a three-field photometer. Crossspectral analysis of the data was used to extract frequencies and horizontal trace velocities of periodic structures. Structures in the λ630 nm emission were characteristic of large-scale waves, and those in the λ558 nm emission were characteristic of medium-scale waves. The results showed distinct polarisation of the propagation azimuths; waves in the λ630 nm emission propagated approximately northwestward throughout the 8 yr period, whilst propagation azimuths of waves in the λ558 nm emission appeared to be solar-cycle-dependent. It is suggested that waves observed in the λ630 nm emission were of predominantly auroral electrojet origin, whilst those observed in the λ558 nm emission were of both auroral and tropospheric origin.