Remote diagnostic of the heliospheric termination shock using neutralized post shock pick-up ions as messengers

Hydrogen pick-up ions when produced in the inner heliosphere are convected outwards with the solar wind and are accelerated by nonlinear wave-particle interactions. Upon their arrival at the solar wind termination shock the h ighest percentage of them passes over from the preshock to the postshock pl asma regime. At this occasion these ions suffer a characteristic change in their density and velocity distribution which sensitively reflects the shoc k properties. We calculate the postshock pick-up ion spectrum and demonstra te the influence of the density compression factor realized at the shock. W e then calculate the distribution function of keV-Energetic Neutral PI-Atom s (H-ENAs) originating as products of these postshock pick-up ions decharge d by local H-atoms and show how, by detection of spectral H-ENA fluxes at t he earth's orbit, a very efficient remote diagnostic of the shock propertie s, especially the shock compression ratio, is enabled. ENAs up to energies of 5 keV clearly reflect the preshock plasma conditions, those at energies larger than 10 keV the postshock plasma conditions. In the energy range bet ween 5 through 50 keV decharged H+ pick-up ions strongly dominate over all competing ENA fluxes which were discussed in the literature up to now.