IMAGE/LENA Observations of Neutral Atoms from the Solar Wind

M. R. Collier (NASA/Goddard Space Flight Center), T. E. Moore (NASA/GSFC), K. W. Ogilvie  
(NASA/GSFC), D. Chornay (NASA/GSFC), J. Keller (NASA/GSFC), S. Boardsen (NASA/GSFC), J. Burch 
(SwRI), B. El Marji (NASA/GSFC), M.-C. Fok (NASA/GSFC), S.A. Fuselier (LMATC), A.G. Ghielmetti 
(LMATC), B.L. Giles (NASA/GSFC), D.C. Hamilton (U. of Maryland), B. Peko (DU), J.M. Quinn 
(U of New Hampshire), T. Stephen (DU), G.R. Wilson (MRC) and P. Wurz (U of Berne)

We report observations of neutral atoms from the solar wind in the Earth's vicinity with the 
Low Energy Neutral Atom (LENA) imager on the IMAGE spacecraft. This instrument, unlike most 
other neutral atom imagers, was specifically designed to be capable of looking at and in the 
direction of the Sun. Observed enhancements in the hydrogen count rate in about the solar 
direction are correlated with neither solar ultraviolet emission nor suprathermal particles 
and must therefore be due to neutral particles from the solar wind. Based on the presence of 
sputtered oxygen observed in the tof spectra, the energy of these neutral particles exceeds 
~1 keV, consistent with solar wind-like energies. In addition, the sputtered oxygen abundance 
tracks the solar wind speed, even when IMAGE resides deep inside the magnetosphere. We 
consider various sources of these neutral particles including solar wind charge exchange 
with dust grains and interstellar neutrals, undisturbed solar wind and magnetosheath charge 
exchange with the Earth's geocorona and solar wind charge exchange with the Earth's geocorona 
in the cusp region.

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