HR: 11:35h
AN: SA22A-06    [Abstracts]
TI: Hemispheric asymmetries in the longitudinal structure of the low-latitude nighttime ionosphere
AU: * McDonald, S E
EM: sarah.mcdonald@nrl.navy.mil
AF: Naval Research Laboratory, Code 7643 4555 Overlook Ave., SW, Washington, DC 20375, United States
AU: Dymond, K F
EM: kenneth.dymond@nrl.navy.mil
AF: Naval Research Laboratory, Code 7643 4555 Overlook Ave., SW, Washington, DC 20375, United States
AU: Summers, M E
EM: msummers@physics.gmu.edu
AF: George Mason University, Department of Physics and Astronomy, Fairfax, VA 22030, United States
AB: Several recent studies suggest that non-migrating diurnal tides generated by tropical weather in the troposphere influence the longitudinal morphology of the low latitude F region ionosphere; in particular, a wave number four pattern is observed in the peak densities and magnetic latitudes of the equatorial anomaly. It is suspected that this variability is driven by E region processes on the dayside. Observations made with the Low Resolution Airglow and Aurora Spectrograph (LORAAS), which flew aboard ARGOS from May 1999 to April 2002, show additional evidence of periodic variations in the densities and latitudes of the equatorial anomaly crests. In this investigation, electron density profiles are reconstructed from limb scans of OI 135.6 nm emissions to obtain maps of the NmF2 at 0230 LT. Our findings show that the longitudinal variability of the NmF2 of the northern anomaly crest matches that of other global observations, but there is a pronounced hemispheric asymmetry in the longitudinal variations observed in the southern anomaly crest. We show that this asymmetry is tied to longitudinal variations in the neutral winds at F region altitudes, which act to enhance the observed wave number four pattern. We discuss the role of the neutral winds by comparing the LORAAS results to both empirical (IRI-90) and physics-based models (SAMI3).
DE: 2415 Equatorial ionosphere
DE: 2427 Ionosphere/atmosphere interactions (0335)
DE: 2437 Ionospheric dynamics
SC: SPA-Aeronomy [SA]
MN: 2007 Fall Meeting