Low energy neutral atoms in the magnetosphere

We report observations of low energy neutral atoms (LENA) from the solar wi nd and the ionosphere, obtained by the LENA Imager on the IMAGE spacecraft. The LENA Imager detects and images LENAs arriving at the spacecraft from w ithin a 90 degrees field of view (8 degrees x8 degrees pixels), swept throu gh 360 degrees every two minutes by spacecraft spin. Neutral atoms arriving at the sensor are converted to negative ions by a conversion surface. The resulting negative ions are separated in energy (3 bins, 10 - 250 eV) and a rrival direction (+/-45 degrees). They are then accelerated, detected, and time-of-flight mass analyzed. The solar wind and the ionosphere both emit m easurable neutral atom fluxes, the latter responding rapidly to to variatio ns of the former.