Hj. Fahr et G. Lay, Remote diagnostic of the heliospheric termination shock using neutralized post shock pick-up ions as messengers, ASTRON ASTR, 356(1), 2000, pp. 327-334
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.