Characterization of Earth's FUV dayglow using the IMAGE FUV imagers

T. J. Immel (1), R. Gladstone (2), S. B. Mende (1), and H. U. Frey (1)

1 - Space Science Laboratory, Berkeley, CA
2 - Southwest Research Institute, San Antonio, TX

The suite of IMAGE FUV instruments is aimed primarily at monitoring auroral emissions. The Wideband 
Imaging Camera (WIC) is designed to study the Lyman-Birge-Hopfield band emission of N2 in the 140-190-nm 
range, while the Spectrographic Imager (SI) detector spectrally separates and images the 135.6-nm doublet 
of OI. These emissions are also ever-present in the terrestrial dayglow, where they are excited mainly by 
photoelectron impact.  Characterization of these dayglow emissions is necessary for investigations of 
auroral emissions where the studied portions of the aurora are sunlit.  Various modeling techniques can 
provide a reasonable characterization of dayglow emissions for such studies.  Furthermore, these can aid 
in in-flight calibration and flat-fielding of the 2D data products. However, changes in Earth's FUV 
dayglow caused by variations in photoelectron energy spectrum or thermospheric composition can be 
difficult to model, requiring a more extensive and careful treatment. In this study, the variability of 
the 135.6-nm and LBH emissions in the first several months of the IMAGE mission is discussed. The 
pertinence of these dayglow variations to auroral and thermospheric studies is also addressed.

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Presented at the Fall American Geophysical Union Meeting, 
San Francisco, CA., December 15-19, 2000