The Effects of a κ‐Distribution in the Heliosheath on the Global Heliosphere and ENA Flux at 1 AU

Abstract

In this paper we investigate heliosheath energetic neutral atom (ENA) fluxes at keV energies, by assuming that the heliosheath proton distribution can be approximated using a κ-distribution. The choice of the κ-parameter derives from observational data of the solar wind (SW). Our work has direct applications to the upcoming IBEX mission, since we generate all-sky ENA maps within the IBEX energy range (10 eV-6 keV), as well as ENA energy spectra in several directions. We find that the use of κ, as opposed to a Maxwellian, gives rise to greatly increased ENA fluxes above 1 keV, while medium-energy fluxes are somewhat reduced. We show how IBEX data can be used to estimate the spectral slope of the proton distribution in the heliosheath, and that the use of κ reduces the differences between ENA maps at different energies. We also investigate the effect that introducing a κ-distribution has on the global interaction between the SW and the local interstellar medium (LISM), and find that there is generally an increase in energy transport from the heliosphere into the LISM, due to the modified profile of ENA energies. This results in a termination shock that moves out by 4 AU, a heliopause that moves in by 9 AU, and a bow shock 25 AU farther out, in the nose direction.