Equatorial and low latitude thermospheric winds: Measured quiet time variations with season and solar flux from 1980 to 1990

Abstract

Thermospheric winds have been systematically determined at Arequipa, Peru, and Arecibo, Puerto Rico, from Fabry‐Perot interferometer measurements of Doppler shifts in the nightglow 630 nm line. The wind databases (1983 – 1990 at Arequipa and 1980 – 1990 at Arecibo) have been edited to eliminate measurements during geomagnetically disturbed conditions, then sorted by season and solar flux level. Following this, they were averaged to obtain the climatological behavior of the nighttime wind variations at the two locations. A new averaging technique, multivariate regression analysis, has been applied to the data, and the results compared to our prior binning averages. The observed wind behaviors at the Arequipa and Arecibo Observatories, which are at equal geographic latitudes on opposite sides of the equator, are contrasted to establish the seasonal flow patterns. The regression analysis results have then been compared with the predicted behavior provided by the National Center for Atmospheric Research's Thermosphere‐Ionosphere‐Electrodynamics General Circulation Model. In many cases, qualitative agreement between measurements and predictions is found as to wind directions and temporal variations, with differences in magnitude of ∼0–50 m/s. However, some striking differences are found that may arise from ionosphere‐thermosphere coupling effects. The overall results provide an important step in establishing the climatology of the thermospheric winds at equatorial and low‐latitude sites.