Abstract
The Interstellar Boundary Explorer (IBEX) mission discovered the presence of a global structure in energetic neutral atom emissions from the outer heliosphere not predicted by any model—the IBEX “ribbon.” In the search for possible explanations, observations have pointed to a likely source from neutral atoms produced through charge exchange with the outflowing solar wind, the secondary solar wind, which then undergoes charge exchange again beyond the heliopause within the very local interstellar medium. Here we study the plasma structure beyond the heliopause created from a range of secondary neutral atom sources: (1) solar wind atoms, (2) pickup atoms inside the termination shock, and (3) suprathermal atoms from the inner heliosheath, between the termination shock and heliopause. All of these particle sources populate the plasma environment beyond the heliopause. At the high end of the observational energy range of IBEX (3.1–6.0 keV FWHM), the significantly broadened and positionally shifted energetic neutral atom signature of the ribbon suggests plasma structure associated primarily with secondary suprathermal atoms from the inner heliosheath. The population created from this suprathermal population extends well above 6 keV (the top of the IBEX energy range) and provides a source for an extremely broad (>60° in angular) width shifted southward (>10°) in latitude from the direction centered on the local interstellar magnetic field. Thus, the extension of plasma structure to energies above IBEX provides a unified explanation of the ribbon created primarily from secondary solar wind atoms to a broadened and shifted structure (the broad ribbon or belt) created primarily from secondary suprathermal atoms in the heliosheath.
