Satellite observations of thermospheric wave 4 at high latitudes

Abstract

Satellite observations of the ionosphere and thermosphere routinely reveal a zonal wavenumber 4 pattern in longitude. In the equatorial region, this is attributed primarily to the eastward propagating non-migrating diurnal tide of zonal wavenumber 3 known as DE3. In this report, the wave 4 is identified using daytime thermospheric airglow emission of atomic oxygen at 557.7 nm emitted from the O(1S) level, using the WIND imaging interferometer (WINDII), launched on NASA’s upper atmosphere research satellite (UARS) in 1991. Waves in the airglow emission rate are attributed to variations in the number density of atomic oxygen, but the WINDII interferometer also sees wave 4 in thermospheric winds from the phase shifts of the emission. What is new in this report is the observation of the wave 4 at high latitudes, where it has not been detected before. The characteristics are described and the possible influences discussed.