Spatial variation of pickup proton energy spectra in the inner heliosheath and fluxes of energetic neutral atoms Original Research Article

The spatial variation of pickup protons downstream the termination shock in the upwind direction is considered taking into account stochastic pre-acceleration in the supersonic solar wind. It is shown that energy spectra of pick-up protons in the inner heliosheath are considerably different from those in the region inside the termination shock due to efficient charge exchange reactions between the protons and interstellar hydrogen atoms and due to energy diffusion. Differential fluxes of energetic neutral atoms (ENAs) originating from the charge exchange process in the inner heliosheath are calculated at 1 AU. It is shown that observations of neutral hydrogen fluxes in the energy range from 1 to 100 keV can give important information on the level of solar wind turbulence in the inner heliosheath.