HR: 14:40h
AN: SA23B-05    [Abstracts]
TI: Remote Sensing of molecular oxygen densities and temperatures in the thermosphere using Stellar Occultation Techniques
AU: Ghosh, S
EM: ron.ghosh@jhuapl.edu
AF: The Johns Hopkins University Applied Physics Laboratory, 11100 Johns Hopkins Road, Laurel, MD 20723
AU: * Yee, J
EM: sam.yee@jhuapl.edu
AF: The Johns Hopkins University Applied Physics Laboratory, 11100 Johns Hopkins Road, Laurel, MD 20723
AU: DeMajistre, R
EM: robert.demajistre@jhuapl.edu
AF: The Johns Hopkins University Applied Physics Laboratory, 11100 Johns Hopkins Road, Laurel, MD 20723
AU: Gibson, S T
EM: stephen.gibson@anu.edu.au
AF: Australian National University, Research School Physic Science, UV Physics Unit, Canberra, ACT 0200 Australia
AU: Lewis, B
EM: brenton.lewis@anu.edu.au
AF: Australian National University, Research School Physic Science, UV Physics Unit, Canberra, ACT 0200 Australia
AU: Dalgarno, A
EM: adalgarno@cfa.harvard.edu
AF: Harvard-Smithsonian Center for Astrophysics, 60 Garden St., Cambridge, MA 02138
AU: Naduvalath, B
EM: naduvala@unlv.nevada.edu
AF: University Nevada Los Vegas, 4505 Maryland Pky, Las Vegas, NV 89154
AU: Yoshino, K
EM: kyoshino@cfa.harvard.edu
AF: Harvard-Smithsonian Center for Astrophysics, 60 Garden St., Cambridge, MA 02138
AB: In this paper we present the results of stellar occultation observations in the thermosphere by the MSX/UVISI instrument. The extinction of stellar spectral signals in the O$_2$ Schumann-Runge continuum ($<$175 nm) provides a remote sensing tool to measure the O$_2$ number density profile in the thermosphere. The density profile then can be used to infer the thermospheric temperature under diffusive equilibrium assumption. Since the thermosphere has a large temperature gradient, increasing from 200K in the lower thermosphere up to $>$1000K in the upper thermosphere, accurate knowledge of the Schumann-Runge continuum cross sections as a function of temeperature is required. MSX/UVISI conducted over 50 UV stellar occultation experiments, covering a range of solar activities. In this paper, we use two sets of theoretically calculated cross-sections to retrieve the thermospheric O$_2$ density and temperature profiles. Comparisons with MSIS and NRLMSIS model prediction are made and differences between observations and model predictions are assessed. The accuracy of the temperature dependence of the O$_2$ absorption cross secctions will be evaluated based on the goodness of the fits to the observed occultation transmission spectra.
DE: 0350 Pressure, density, and temperature
DE: 0355 Thermosphere--composition and chemistry
DE: 0394 Instruments and techniques
SC: SPA-Aeronomy [SA]
MN: 2004 AGU Fall Meeting