Observation of the electron and proton aurora from the IMAGE satellite: comparison with 
in-situ particle precipitation

J.-Cl. G'erard (1), B. Hubert (1), M. Meurant (1), V. Coumans (1), S. Mende (2), H. Frey (2), 
V.I. Shematovich (3), D.V. Bisikalo (3), G. R. Gladstone (4), S. Habraken (5)

1 - LPAP, Universite de Liege, Belgium}
2 - SSL, University of California at Berkeley
3 - Institute of Astronomy, Moscow
4 - SWRI, San Antonio, Texas, USA
5 - CSL, Universite de Liege, Belgium

The FUV instrument on the IMAGE satellite images the aurora in three different spectral regions.  
The Wideband Imaging Camera (WIC) observes the molecular N2 LBH and atomic nitrogen emissions at 
140-190 nm.  The two channels of the Spectrographic Imager (SI) observe the Doppler shifted 
Lyman-alpha emission of precipitating protons at 121.8 nm (SI12) and  electron-produced emission 
from OI at 135.6 nm (SI13). Observations made with the  WIC and the SI cameras make it thus 
possible to spectrally discriminate between the proton and electron FUV aurora.  Data collected 
since early May 2000 show that all three instruments make very sensitive measurements with high 
spatial resolution even in the sunlit daytime cusp.  It was  demonstrated that  the SI12 channel 
is capable for the first time to map the energetic protons.

Observations show that electron and proton precipitations roughly overlap.  However, images of 
the Doppler-shifted Lyman-alpha emission show clear morphological differences  between the 
diffuse proton aurora and the more structured electron precipitation. Regions such as the 
pre-midnight low latitude sector where proton precipitation dominates may be separated from the 
electron component.

Parallel in-situ observations of the precipitated particles have been collected from low-altitude 
satellites during IMAGE apogee observations of the North polar region. These simultaneous 
measurements permit a comparison between the remotely imaged particle precipitation and the 
magnetic footprint measurements made along the low-altitude satellite track. The local and  
global precipitated energy fluxes of both protons and electrons estimated from both types of 
observations will be compared as well as the precipitation boundaries. 

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Presented at the European Geophysical Society meeting, 
Nice, France, March 30, 2001