Neutral Hydrogen Density Profiles Derived from Geocoronal Imaging

Ostgaard, N., S. B. Mende, H. U. Frey, G. R. Gladstone,

The geocorona is produced when solar Ly-a radiation is resonance scattered
by  neutral hydrogen in the exosphere and measurements of the geocoronal
intensity from space can therefore be used to derive the density profile of
neutral hydrogen surrounding the Earth. The Geocorononal Imager (GEO)
instrument, which is part of the FUV imaging system onboard the IMAGE
satellite, is designed to measure the geocoronal Ly-a emissions. Three
imagers, HENA, MENA and LENA onboard the IMAGE satellite are imaging the
energetic neutral atoms (ENA). ENA are produced by charge exchange between
energetic magnetospheric ions  and the cold neutral hydrogen background. In
order to convert the measurements of ENA to magnetospheric ion distribution,
information about the instantaneous neutral hydrogen density distribution is
needed. In this paper we present how we can develop an inversion scheme
using the GEO data of Ly-a column density to obtain the radial density
profile of the neutral hydrogen in the magnetosphere. 

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To be presented at the Magnetospheric Imaging Workshop, 
Yosemite National Park, California, U.S.A., Feb. 5-8, 2002.