Remote diagnostic of the solar-cycle-induced heliospheric interface variation using energetic neutral atoms

The region of perturbed plasma flows between the supersonic solar wind and the supersonic interstellar plasma is generally called the heliospheric interface. This extended plasma region at the boundary of the heliosphere, though theoretically thoroughly studied and revealed as strongly time-variable during the solar activity cycle, is up to the present not accessible by direct or remote observations. Here we emphasize the possibility to remotely investigate this time-variable region by imaging it through energetic neutral atoms. We calculate the time-dependent distribution function of keV-energetic neutral H-atoms originating as products of charge exchange reactions between H-atoms and protons in the interface region. By carrying out line-of sight integrations of time-variable spectral sources of energetic neutral H-atoms we estimate their fluxes for an earth-bound detector as function of time within the solar activity cycle. Our predictions can directly be taken as a basis for the interpretation of planned heliospheric ENA-measurements upcoming in the near future