HR: 1340h
AN: SA33A-1060    [Abstracts]
TI: Thermospheric Wind Gradients and Horizontal Divergence Measured During the HEX-1 Rocket Mission
AU: * Conde, M G
EM: mark.conde@gi.alaska.edu
AF: Geophysical Institute University of Alaska Fairbanks, 903 Koyukuk Drive, Fairbanks, AK 99775, United States
AU: Larsen, M F
EM: mlarsen@clemson.edu
AF: Department of Physics and Astronomy, 118 Kinard Laboratory Clemson University, Clemson, SC 29634, United States
AU: Wescott, E M
EM: gene.wescott@gi.alaska.edu
AF: Geophysical Institute University of Alaska Fairbanks, 903 Koyukuk Drive, Fairbanks, AK 99775, United States
AU: Lummerzheim, D
EM: lumm@gi.alaska.edu
AF: Geophysical Institute University of Alaska Fairbanks, 903 Koyukuk Drive, Fairbanks, AK 99775, United States
AU: Stenbaek-Nielsen, H
EM: hnielsen@gi.alaska.edu
AF: Geophysical Institute University of Alaska Fairbanks, 903 Koyukuk Drive, Fairbanks, AK 99775, United States
AB: On March 25, 2003, three trimethyl-aluminum trails were deployed by rockets near a stable pre-midnight auroral arc lying 400 km north of Poker Flat, Alaska. Drift of these trails over time yielded wind measurements in the height range 120 km to 180 km. The trail geometry allowed direct height-resolved measurements of all three wind components, as well as their meridional and vertical gradients. Although zonal gradients of the three wind components were only directly measured at one height, the zonal gradient of zonal wind could be inferred indirectly, using the equation for mass conservation. Our analysis yielded horizontal divergence estimates up to 0.002 s^-1, which is surprisingly large given that very quiet geomagnetic conditions prevailed. As a possible mechanism, we examine the hypothesis that the observed wind perturbations are primarily the signature of a monochromatic field of plane gravity waves, propagating approximately geomagnetically westward along the auroral oval, and parallel to the background wind. We show that a plane monochromatic perturbation obeying the gravity wave dispersion and polarization relations can be fitted to match, in most cases, the amplitudes and phases of the observed wind components and of the inferred horizontal divergence. Although the wind perturbation amplitudes are large (22 m s^-1 vertically and 75 m s^-1 horizontally) the inferred wave parameters are well within the ranges observed previously. Further, because the calculated dissipation time constant for the fitted perturbation is long compared to the wave period, the inferred wave field is one that could reasonably exist at these heights.
DE: 0310 Airglow and aurora
DE: 0358 Thermosphere: energy deposition (3369)
DE: 2427 Ionosphere/atmosphere interactions (0335)
DE: 3384 Acoustic-gravity waves
SC: SPA-Aeronomy [SA]
MN: 2007 Fall Meeting