Simultaneous Measurements and Monthly Climatologies of Thermospheric Winds and Temperatures in the Peruvian and Brazilian Longitudinal Sectors

The nocturnal variations of the equatorial thermospheric winds and temperatures are studied by comparing the wind and temperature responses for two longitudinal regions separated by similar to 38 degrees(similar to 4200 km) for selected nights with simultaneous measurements as well as monthly climatologies. The Fabry-Perot observations of thermospheric winds and temperatures were made from Jicamarca (11.96 degrees S, 76.86 degrees W) on the west coast of Peru at the geomagnetic equator and from the northeastern region of Brazil (7.0 degrees S, 36 degrees W) located similar to 7 degrees south of the geomagnetic equator. Comparisons of the zonal wind data for both sectors on individual nights and monthly climatologies for the September equinoctial months revealed a consistent and similar pattern of behavior characterized by a slow eastward zonal wind, similar to 40-50 ms-1, near evening twilight, then a steady increase to a peak speed near 21-22 LT that was then followed by a slow decay toward dawn when an eastward increase to 40-50 ms-1 was seen near 04-05 LT. The maximum peak speeds for Peru and Brazil were 130-140 ms(-1) and 80-90 ms(-1), respectively. These results were compared with model nighttime zonal wind variations computed using the empirical Horizontal Wind Model recently updated by the Naval Research Laboratory. Good agreement between the model variations and observations was generally found. The data from both sectors showed the meridional wind behavior to be dominated by a double-peaked structure with the two peaks of equatorward (northward) winds separated by similar to 6 hr. The Universal Time difference between the Peru and Brazil meridional wind structures was comparable with the solar time difference of 2.5 hr between the two sectors suggesting that the meridional winds were dominated by the migrating tidal wave. The comparison of the Peru and Brazil nighttime temperature variations showed the development of a midnight temperature maximum (MTM) near local midnight. Relative to the Naval Research Laboratory Mass Spectrometer Incoherent Scatter empirical model (NRLMSISE-00) baseline for both sectors, the MTM peak amplitudes were within the range of 50 K to 100 K, with the MTM peak occurring similar to 1 hr after the time of the first northward peak of the meridional wind structure. This phase offset is interpreted to be the time lag of the tidal-wave temperature fluctuation relative to the meridional wind increase northward as the wind and temperature portions of the tidal wave propagate from below into the thermosphere. Key Points: Thermospheric zonal neutral winds faster in Peru than in Brazil Meridional winds for both Peru and Brazil sectors show semi-diurnal tidal signatures Midnight temperature maximum similar in structure for both Peru and Brazil sectors