Fabry-Perot Studies of Equatorial Thermospheric Dynamics and Composition

Clemson University, Clemson SC

Investigators

Abstract

In this project funds are requested to continue studies of the equatorial thermospheric dynamics using the upgraded automated Arequipa Fabry-Perot interferometer (FPI) observatory operating at Arequipa which is ~400km south of the magnetic equator. The instrumental upgrade increase of the FPI sensitivity by a factor of 15 is achieved by replacing the GaAs photomultipler with a back-thinned CCD detector. The improved sensitivity of the Arequipa FPI will be used to extend current studies of the midnight temperature maximum and the equatorial wind and temperature anomaly (EWTA) with increased accuracy. A new line of research is proposed that would be based upon the observations of O+ and OH airglow emissions for the study of thermospheric [O]. The Doppler widths of the O+ spectral feature would provide information regarding the possible production of the hot oxygen corona that was previously observed with this technique in 1980. If such hot [O] atoms exist near the equatorial upper thermosphere and exobase, aside from an increase in the effective Doppler width to equivalent temperatures of ~4000, an excess of a few Rayleighs of 732nm emission rate relative to the FLIP predictions normalized by the observations at earlier solar depression angles should be seen. The proposed 732 nm measurements may resolve the question as to whether there exists and influx of fast oxygen ions into the equatorial ionosphere from the magnetosphere, which has been suggested to be caused by the polar O+ outflow that is diverted to the low latitude ionosphere by magnetospheric-ionospheric coupling processes. During the night the Doppler shifts of the OH nightglow at 731.6 nm would be observed to determine mesospheric winds averaged over the OH volume emission profile with a centroid altitude of ~87km. These results would be particularly useful in the support of the TIMED (thermosphere ionosphere mesosphere energetics and dynamics) satellite tidal studies as ground-based observations of mesospheric tidal winds in the Southern hemisphere are sparse. A filter changer would select between the two filters, 630 nm and 732 nm, as necessary to get the observations these science objectives require.