Low Energy Neutral Atoms in the Magnetosphere 

T.E. Moore, M. R. Collier, D. Chornay, B.L. Giles [NASA/GSFC/LEP, 
Code 692, Greenbelt, MD 20771, USA, thomas.e.moore@gsfc.nasa.gov]
S. A. Fuselier A. Ghielmetti [Lockheed Martin Co., Palo Alto, CA USA]
D. C. Hamilton, B. El Marji[University of MD, College Park, MD USA]
J. M. Quinn [University of New Hampshire, Durham, NH USA]
T. M. Stephen [University of Denver, Denver, CO USA]
P. Wurz [University of Bern, Bern, SWITZERLAND]
G. R. Wilson [Mission Research Corp., Nashua, NH USA]

We report observations of low energy neutral atoms from both the solar 
wind and the terresrial ionosphere, obtained by the Low Energy Neutral 
Atom Imager on the IMAGE spacecraft. The LENA Imager detects and images 
fast neutral atoms arriving at the spacecraft from within a 90 deg 
field of view, swept through 360 deg by spacecraft spin with a 2 min 
period. Arriving neutrals are converted by reflection from a solid 
surface to negative ions. These are coarsely separated in energy 
(10 - 250 eV in the mode used most to date) and arrival direction 
(+/- 45 deg). They are then accelerated and detected as they pass 
through a thin foil and strike an image plane detector. Time-Of-Flight 
measurement between foil and detector yields the ion mass. We find that 
the both the solar wind and the ionosphere emit fluxes that routinely 
exceed our sensitivity level. Fluxes from the sun are observed to be 
modulated in response to solar wind variations, as are ionospheric 
outflow fluxes. Several periods of high geomagnetic activity have been 
observed, most produced by coronal mass ejecta. The largest fluxes are 
observed from the polar auroral regions during perigee passes over the 
southern pole. The range of LENA observations during the first few 
months of IMAGE operations are described and summarized. 

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