HR: 1340h
AN: SA43A-1093    [Abstracts]
TI: The High-Latitude Knee of the O/N2 Ratio Profile: Latitudinal Variations with UT, Local Time, Season, and Magnetic Activity
AU: * Craven, J D
EM: craven@gi.alaska.edu
AF: University of Alaska Fairbanks, Geophysical Institute, 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: rmeier@gmu.edu
AF: School for Computational Sciences, George Mason University, Fairfax, VA 22030 United States
AU: Paxton, L J
EM: larry.paxton@jhuapl.edu
AF: JHU/Applied Physics Laboratory, 11100 Johns Hopkins Rd, Laurel, MD 20723 United States
AU: Strickland, D J
EM: dstrick@cpi.com
AF: Computational Physics, Inc., 8001 Braddock Rd., Suite 210, Springfield, VA 22151 United States
AB: Repeated observations with DE-1, TIMED, and other spacecraft have established that transient decreases in the thermospheric O/N2 ratio at subauroral latitudes in the morning sector are associated in increased auroral and geomagnetic activity. These composition changes then directly affect F-region electron densities. An investigation with the GUVI instrument in the TIMED mission has attempting to demonstrate by direct observation a causal relation between these altered compositions with air movements from the early morning hours, but it has proved difficult due in part to the nature of the spacecraft orbit. Early attempts have been replaced by a more global effort to first analyze the O/N2 ratio and its variations with UT, local time, season, and magnetic activity. It is anticipated that better understanding of the influence of the first three parameters will provide a cleaner database with which to seek out the original objective. The current effort and results, which will be discussed in this paper, focus on the analysis of GUVI observations spanning the first several years of the TIMED mission. The initial emphasis is on the most clearly defined signature of most O/N2 latitudinal profiles in each orbit, the reasonably sharp transition, or knee, from the low-latitude, relatively constant values of O/N2 to the much lower values poleward of the knee. The motion of the knee to lower latitudes with increased magnetic activity is well established in a qualitative sense. The objective is a more quantitative analysis for which the magnetic-activity-driven variations are unencumbered at a fixed local time, for example, by UT and season.
DE: 0310 Airglow and aurora
DE: 0355 Thermosphere: composition and chemistry
DE: 2790 Substorms
SC: SPA-Aeronomy [SA]
MN: Fall Meeting 2005