Studying the Heliosphere in Energetic Neutral H and He Atoms above 30 keV/amu

Energetic neutral atoms (ENA) are energetic ions neutralized by charge exchange with atoms in an ambient gas. The dynamics of charge exchange and the neutrality of ENA allow their sue to sample the mass and energy distributions of the ion population in regions of ENA production far away across magnetic fields. For ENA of energies > 30 keV/amu in the heliosphere, the energetic ions include anomalous cosmic rays in the heliosheath and pickup ions accelerated in interplanetary shocks; and the ambient gas is the neutral component of the local interstellar medium that permeates the heliosphere. ENA provide unique access to all regions of the heliosphere. We review some aspects of using ENA of energies > 30 keV/amu to study the heliosphere and suggest what can be done to fully utilize ENA in gaining a global view of the different particle populations linked by the acceleration and transport processes in the heliosphere.