Energetic neutral atom imaging of magnetospheric ions from high- and low-altitude spacecraft

Abstract

We present a mapping from the 2-dimensional images formed by energetic neutral atoms (ENAs) to the phase space of physically relevant parameters of the energetic ion distributions that generate the images. This mapping of the lines of sight (LOS) for each image pixel into the L-MLT plane reveals the manner in which the LOS probe the spatial volume of the ion distribution as well as the configuration of its boundaries. Thus this mapping has direct application to the unfolding of ENA images obtained from both high- and low-altitude spacecraft.