Comparison of the Modeled 135.6 nm Auroral Emission to TIMED GUVI Observations: Mapping Thermospheric Composition Variations During Auroral Events Above Alaska and Northwest Canada

Details Comparison of the Modeled 135.6 nm Auroral Emission to TIMED GUVI Observations: Mapping Thermospheric Composition Variations During Auroral Events Above Alaska and Northwest Canada Comparison of the Modeled 135.6 nm Auroral Emission to TIMED GUVI Observations: Mapping Thermospheric Composition Variations During Auroral Events Above Alaska and Northwest Canada

Dec 2003

adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=2003agufmsa21a..05k&link_type=abstract

American Geophysical Union, Fall Meeting 2003, abstract #SA21A-05

Physics

0310 Airglow And Aurora, 0355 Thermosphere: Composition And Chemistry, 0358 Thermosphere: Energy Deposition, 2407 Auroral Ionosphere (2704), 2435 Ionospheric Disturbances

Scientific paper

Satellite imaging of the far ultraviolet (FUV) aurora provides not only the opportunity to infer characteristics of the precipitating auroral electrons (energy flux and mean energy), but also the relative abundance of thermospheric neutral constituents compared to model estimates. Using TIMED GUVI observations of the molecular nitrogen LBH-Long (165-180 nm) and -Short (140-150 nm) auroral emissions, we derive horizontal maps of the energy flux and mean energy parameters. With these, we derive the modeled atomic oxygen 135.6 nm emission, which is then compared to GUVI 135.6 nm observations. From this comparison, we derive a third parameter referred to as the column shift, which varies the 135.6 nm model [Lummerzheim and Lilensten, 1994] estimate by shifting the MSIS-90 [Hedin, 1991] model [O] / [N2] ratio up or down while maintaining total mass density at each altitude (pressure level), subsequently redistributing the O and N2 densities at each altitude. Thus, the column shift, which acts as a composition perturbation in the model in the vertical direction, may represent a real thermospheric composition disturbance in the vertical direction. With this in mind, Fabry-Perot spectrometer (FPS) measurements of lower thermospheric vertical winds and temperatures obtained in Alaska and Northwest Canada are compared with the column shift parameter to determine any possible correlations. Some new statistical properties of the column shift, based on this analysis as applied to POLAR UVI data as well as GUVI data, are also presented. Hedin, A. E., Extension of the MSIS thermosphere model into the middle and lower atmosphere, J. Geophys. Res., 96, 1159-1172, 1991. Lummerzheim, D. and J. Lilensten, Electron transport and energy degradation in the ionosphere: evaluation of the numerical solution, comparison with laboratory experiments and auroral observations, Ann Geophysicae, 12, 1039-1051, 1994.

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