Low energy neutral atoms in the magnetosphere

Abstract

We report observations of low energy neutral atoms (LENA) from the solar wind and the ionosphere, obtained by the LENA Imager on the IMAGE spacecraft. The LENA Imager detects and images LENAs arriving at the spacecraft from within a 90° field of view (8°× 8° pixels), swept through 360° 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 - 250eV) and arrival direction (±45°). They are than accelerated, detected, and time-of-flight mass analyzed. The solar wind and the ionosphere both emit measurable neutral atom fluxes, the fluxes, the latter responding rapidly to variations of the former.