REMOTE IMAGING OF ION DISTRIBUTIONS USING LOW-ENERGY NEUTRAL ATOMS

The scope of the neutral atom imaging instrument on the proposed HI-LI TE mission is to study the instantaneous global distribution of the lo w energy ion outflow from the high latitude auroral region, and its la rge scale temporal evolution with solar and geomagnetic activity by de tecting neutral atoms, produced through charge exchange between the ou t flowing ions and the neutral atmosphere. The proposed instrument wil l record maps of energy and mass flux of the source region. For satisf actory performance, high ionization efficiency for the two species of principal interest, H and O, in the energy range of 10 eV to 300 eV is required. To achieve this, surface ionization will be employed, where a considerable fraction of the reflected primary atoms will be negati vely ionized.