Inner Heliosheath Size and Pressure

Using observations of Energetic Hydrogen Atoms (EHAs) with IBEX and Cassini, proton differential intensities in the heliosheath with Voyagers, and interstellar pickup protons with Ulysses, we deduce the proton velocity distribution from a few keV to ~50 keV as a function of heliocentric distance (R) in the heliosheath. We consider four separate components: (a) the heliosheath (HS) solar wind, (b) HS pickup protons, (c) heliosphere pickup protons and (d) the -5 power law suprathermal tails that combine to produce the composite IBEX-LO, IBEX-HI and Cassini INCA EHA spectrum. We find that (1) the total particle pressure in the HS is (1.2 ± 0.15)×10-12 dyne/cm2, with contributions from individual components varying with R; (2) the dominant pressure resides in heliosphere pickup protons throughout most of the HS, and in the suprathermal tails-ACRs near the heliopause (HP); (3) the heliocentric distance of the HP in the Voyager-1 direction, RHS, is 142(+12,-9), 148(+12,-9) and 158(+12,-9) AU using the interstellar neutral H density at the termination shock of 0.115, 0.100 and 0.085 cm-3, respectively, with the lower limits computed using lower limits of the measured EHA differential intensities and assuming that ~30% of the EHAs come from beyond the HP; (4) in order to explain the lowest energy published IBEX EHA flux, the velocity of the compressive turbulence is predicted to start increasing at (RHS - ~10) AU, reaching (155±5) km/s near the HP. The Fisk and Gloeckler model for ACR acceleration near the heliopause requires (2) and (4).