HR: 17:45h
AN: SA34A-08    [Abstracts]
TI: Thermospheric Composition Changes in the Morning Sector near Local Midnight in Association with Substorm Activity and IMF Orientation
AU: * Craven, J D
EM: craven@gi.alaska.edu
AF: Geophysical Institute and Dept. of Physics, University of Alaska Fairbanks, Fairbanks, AK 99775 United States
AU: Christensen, A B
EM: andy.christensen@ngc.com
AF: The Aerospace Corp., PO Box 92957, Los Angeles, CA 90009 United States
AU: Meier, R R
EM: meier@upa2.nrl.navy.mil
AF: School for Computational Sciences, George Mason University 4400 University Drive, Fairfax, VA 22030 United States
AU: Paxton, L J
EM: larry.paxton@jhuapl.edu
AF: JHU/Applied Physics Laboratory, 11100 Johns Hopkins Road, Laurel, MD 20723 United States
AU: Strickland, D J
EM: dstrick@cpi.com
AF: Computational Physics, Inc., 8001 Braddock Road, Suite 210, Springfield, VA 22151 United States
AB: Repeated observations with DE-1 and other spacecraft have established that transient decreases in the far-ultraviolet (FUV) terrestrial OI emissions at subauroral latitudes in the morning sector are associated with decreases in the O/N2 ratio at thermospheric altitudes. These decreases are observed following onset of intense auroral activity and, at northern latitudes near the autumnal equinox, the greater spatial extent and depth of decrease are associated with a positive IMF By component. These changes in thermospheric composition directly affect F-region electron densities. It is believed that the altered composition is driven by aurorally related heating and the antisunward polar jet, which transports heated air to subauroral latitudes in the very early hours of local time and then into the morning sector. FUV observations of this altered composition close to local midnight and in the early morning hours are lacking, due in part to the need for FUV observations in the sunlit hemisphere (i.e., local summer), but are necessary to support this general expectation. Other important influences are also present. The GUVI/TIMED observations at FUV wavelengths are providing an extensive new set of unambiguous thermospheric composition measurements over a wide range of local times and latitudes in both auroral hemispheres as the orbit of the near-polar-orbiting TIMED spacecraft processes rapidly in local time. These data are being scanned in a search for the requisite combination of sampling at the right local times and season in periods of auroral substorms to provide answers to the question of composition changes near local midnight and the early morning hours. A further report on this search and its findings are presented in this paper.
DE: 2435 Ionospheric disturbances
DE: 0310 Airglow and aurora
DE: 0355 Thermosphere--composition and chemistry
DE: 0358 Thermosphere--energy deposition
SC: SPA-Aeronomy [SA]
MN: 2004 AGU Fall Meeting