Observations of Waves in the Far Ultraviolet Emissions from the Thermosphere and Ionosphere: NASA TIMED/GUVI and DMSP/SSUSI

Waves or wave-like features are reported in the observations made by sensors (NASA TIMED/GUVI and DMSP/SSUSI). These sensors are particularly interesting because they operate in the far ultraviolet or FUV (115 to 180nm). These sensors can look in the nadir, and when viewing in the nadir, only see emissions that arise in the thermosphere and ionosphere. These emissions are, of course, column integrated measurements however the contribution functions vary with wavelength due to the change in the excitation mechanism, the pure absorber optical depth and the line center opacity.

All that said, these emissions show wavelike variation in intensity over scales of hundreds to thousands of kilometers with amplitudes of a few percent.

GUVI and SSUSI have been operating for over 20 years. They are in high inclination low Earth orbits (74.1deg, 625km; 98.9deg and 850km, respectively) which provide global coverage.

In this talk we discuss the observations of these waves and their postulated association with lower atmospheric forcing. We will describe the radiative transfer aspects of the emissions that provide us with some useful insights into the altitude dependence of the structure. We will discuss the waves observed in H Lyman alpha, atomic oxygen and molecular nitrogen and their variability and characteristics.