A Statistical Analysis of Secondary Interstellar Neutrals by Using IBEX-lo Sky Maps

A variety of energetic neutral atoms (ENAs) is generated at the various heliospheric interfaces, the inner heliosheath, outer heliosheath (OHS), and the termination shock (TS). Depending on where and how these ENAs are generated, they belong to different energy regimes. While interstellar neutral (ISN) particles flow through the heliospheric boundary is mostly unimpeded, a substantial fraction of ISN H and O is filtered due to charge exchange with ambient plasma ions before reaching the TS. Secondary ISN atoms are generated by the charge exchange reaction between primary ISN atoms and interstellar ions in the outer heliosheath, forming walls of H and O in front of the heliopause (HP). These neutral particles that can be detected at 1AU carry information on the flow around the heliosphere and the physical processes in these boundaries. Due to very different magnitudes of charge exchange cross sections, the main source of the secondary He is charge exchange with the OHS He⁺, while that of the secondary O is the charge exchange between interstellar O⁺ and the OHS H. Therefore, the oxygen results are drastically different from those of helium. To investigate the secondary component of the ISN in detail we need to consult not only the theoretical predicted primary component (Lee at al., 2012) and secondary component (Kubiak et al. 2016) but we also need to provide a statistical analysis of the measured signal. The statistical analysis methods will include background substantiation and Cluster Analysis Method (CAM). In this presentation we will present the results of the secondary ISN populations distributed in space around the heliosphere, its statistical significands, its origin, and its possible generation mechanism.