IMAGE-FUV observations and modeling of proton-induced aurora

B. Hubert and J.C. Gerard, (LPAP, ULg, Liege, B-4000, Belgium; hubert@astro.ulg.ac.be)
V.I. Shematovich, D.V. Bisikalo (Astronomical Institute, Moscow 109017, Russia)
S.B. Mende, H.U. Frey, S.P. Geller, H. Heetderks, M. Lampton (SSL, UCB, Berkeley, CA 94720)
S. Habraken, E. Renotte, C. Jamar and P. Rochus (CSL, ULg, Liege B-4200, Belgium) 

Observations made with the Wide-Band Imaging Camera (WIC) and the Spectrographic Imagers 
(SI) on board the IMAGE satellite make it possible to spectrally discriminate between proton 
and electron FUV aurora. They clearly show that electron and proton precipitations largely 
overlap.  However, images of the Doppler-shifted Lyman-alpha emission show regions such as 
the pre-midnight low latitude sector where proton precipitation is generally separated from 
the electron component.

Simulations based on the statistical DMSP satellite measurements of electron and proton 
precipitation have been made to calculate the induced FUV emissions.  Auroral Lyman-alpha is 
solely excited by energetic protons suffering charge exchange collisions. Lyman-alpha 
emission rates and line profiles are calculated with a Direct Monte Carlo Method. They 
indicate that, at most locations, N2 LBH and OI 135.6 nm excitation is dominated by primary 
and secondary electrons.  Only at certain local times and latitudes do protons and their 
secondary electrons add a significant contribution to these emissions.  Comparison will be 
presented between the expected morphology and brightness distribution based on the 
statistical particle measurements and IMAGE FUV observations.  Large upward fluxes of fast 
hydrogen atoms due to magnetic mirroring, geometric spreading and collisional scattering of 
the precipitated protons are predicted above regions of strong proton precipitation.

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