Solar Wind Impact on ENAs from Earth’s Subsolar Magnetosheath

The solar wind is heated and decelerated by Earth’s bow shock, resulting in a hot and dense population of magnetosheath ions. This increases the production of energetic neutral atoms (ENAs) in this region, which enables the global imaging of Earth’s magnetosheath using ENA imagers onboard the IBEX spacecraft. Furthermore, since these ENAs are unaffected by electromagnetic forces, they carry information about the inherent properties of the progenitor plasma.       
In this work, ENA fluxes from the subsolar magnetosheath, observed by the IBEX spacecraft, are compared to solar wind (SW) conditions. These comparisons reveal that the flux of ENAs is strongly influenced by the SW density, speed, and temperature. Furthermore, evidence of the specularly reflected proton population in the magnetosheath is observed by comparing ENA spectra for different interplanetary magnetic field configurations. This work provides observational constraints to modeling and theoretical work on ENAs from Earth's subsolar magnetosheath and shows that ENAs from Earth's magnetosheath are reflective of their parent ion populations in the magnetosheath.