Key points are not available for this paper at this time.
Energetic neutral atom (ENA) emission is markedly brightest at the lowest altitudes, because it is there that the density of ambient neutrals strongly increases with decreasing height. Analytic expressions are derived in the approximation of single charge-exchange and ionization collisions between energetic ions and exospheric neutrals. The computer simulation of ENA intensities from low altitudes, heretofore requiring Monte Carlo calculations, is thus reduced to a single numerical integral for each line of sight. The attenuation of the incident energetic ions by charge exchange depends strongly on the mirror force, whereas the attenuation of emergent ENA depends on the line-of-sight geometry to the ENA imager. The altitude of maximum ENA emission is a strong function of ion pitch angle and altitude for a given L value of the field line
E. C. Roelof (Wed,) studied this question.