Comparison of heliosphere models with IBEX-Lo observations of Energetic Neutral Atoms at 50 eV - 2 keV energy

The Interstellar Boundary Explorer (IBEX) is a NASA satellite in Earth’s orbit, observing both interstellar neutral atoms entering the heliosphere and energetic neutral atoms (ENAs) from the interstellar boundaries from roughly 10 eV to 6 keV. IBEX consists of two ENA imagers: IBEX-Lo covers the low energy range from 10 eV to 2 keV, IBEX-Hi covers ENA energies between 500 eV and 6 keV (corresponding roughly to solar wind energy).

ENA imaging is an indispensable tool in space physics. ENAs carry information on the plasma region where they were created that can be deciphered by analysis of the species, intensity, spatial distribution, and energy spectrum. The ENA intensity measured by a remote observer, such as IBEX, is a line of sight integral over potentially many different ion populations and local neutral atom densities. Thus, to derive properties of the heliosphere and of its plasma populations from such ENA measurements, they must be compared with the predictions of heliosphere models.

The majority of ENA model comparisons with IBEX observations so far were restricted to IBEX-Hi data. In this study, we present the first comparison of IBEX-Lo data with heliosphere models over one full solar cycle (using the tabulated energy spectra in Galli et al. 2022, http://dx.doi.org/10.3847/1538-4365/ac69c9). We use heliosphere models developed at the Moscow University and Boston University in this study. The comparison concentrates on the energy spectra of heliospheric ENAs originating from regions in the sky (such as Voyager 1, Voyager 2, South Pole, North Pole, and heliosphere downwind direction) that are cardinal directions for the comparison of the ENA data and the global heliosphere models.

This study is a part of the Research Team “Global Structure of the Heliosphere” within the SHIELD NASA DRIVE Science Center.