Low Energy Neutral Atoms as seen from IMAGE

Thomas E. Moore NASA/GSFC

The LENA Imager for the IMAGE mission detects, analyzes, and images fast neutral atoms in the energy range below 1keV. It does so using charged particle deflectors having a 90 x 8 deg. field of view, a 1 cm^1 "pinhole" camera, a grazing incidence conversion surface that creates negative ions from incident fast neutrals, an electrostatic lens and energy analyzer to collect and guide the negative ions, and a 2D imaging time-of-flight system to sort the particles by arrival direction and energy. Early operations indicate that, in addition to the emission of LENA from the Earth during geomagnetically active periods, the instrument routinely observes LENA originating in the solar wind. Enhanced LENA from the solar wind are accompanied by a relatively prompt response of LENA emitted from the Earth, loosely consistent with ionospheric mass ejections that are known to be driven by the arrival of coronal mass ejecta at the Earth. Modeling efforts aimed at interpreting these observations will be briefly described.