HR: 11:50h
AN: SA52A-06    [Abstracts]
TI: New Results on the Midnight Temperature Maximum Near Equatorial Latitudes
AU: * Meriwether, J
EM: meriwej@clemson.edu
AF: Clemson University, Department of Physics and Astronomy 208 Kinard Laboratory, Clemson, SC 29634, United States
AU: Faivre, M
AF: Clemson University, Department of Physics and Astronomy 208 Kinard Laboratory, Clemson, SC 29634, United States
AU: Veliz, O
EM: meriwej@clemson.edu
AF: Jicamarca Radio Observatory, Instituto Geofisico del Peru, Lima, Peru
AB: New observations of the equatorial thermospheric dynamics observed from Arequipa, Peru (16.2 S, 72.4 W) obtained with an imaging Fabry-Perot interferometer during the southern hemisphere winter of 2005 (June- August) show an interesting correlation of the formation of the midnight temperature maximum (MTM) with the strength of the semi-diurnal tidal meridional wind. The observations are obtained in eight azimuthal directions at 60 degree zenith angle. Each direction represents an exposure of 120 s and the Doppler shifts and Doppler broadening are analyzed with uncertainties of 8-10 m/s and 30-35 K, respectively. These results are used to prepare horizontal wind maps. When the amplitude of the meridional flow is weak, there is generally not observed any temperature enhancement near midnight. When the meridional flow equatorward is strong, 50-100 m/s, then there is observed about two hours later a significant increase in temperature of typically 100 K. This time delay between the northward component of the thermospheric wind vector and the peak of the MTM structure is observed to be about 30 minutes for two nights obtained during the spring equinox. These results suggest that the semi-diurnal tidal mode forms the MTM by convergence upon the geographical equator to the north of Arequipa. After the compressional heating has taken place, then there is a return "wave" formed that transports the heated air to the region of Arequipa. The decrease of the time delay between winter and the spring equinox is a result of the convergence region forming closer to Arequipa than during the winter. Observations of the horizontal wind maps over successive nights in early July show that the thermospheric wind structure varies considerably from night to night with a variation in the appearance of the meridional wind structure by several hours from night to night. It is tempting to suggest a relationship between this variability and the production of the equatorial spread-F phenomenon.
DE: 0310 Airglow and aurora
DE: 0350 Pressure, density, and temperature
DE: 3369 Thermospheric dynamics (0358)
DE: 3389 Tides and planetary waves
SC: SPA-Aeronomy [SA]
MN: 2007 Joint Assembly