Seven Years of Imaging the Global Heliosphere with IBEX

TL;DR

This paper presents a comprehensive 7-year analysis of IBEX's ENA observations, revealing the evolution of the Ribbon and GDF in the outer heliosphere and supporting a secondary ENA source explanation.

Contribution

It extends previous IBEX data analysis by including 2014-2015 data, providing a complete 7-year dataset and new insights into heliospheric dynamics and ENA sources.

Findings

The Ribbon has evolved differently than the GDF, with partial recovery.

The Ribbon has lost its latitudinal ordering, indicating solar wind condition changes.

Data supports a secondary ENA source as the explanation for the Ribbon.

Abstract

The Interstellar Boundary Explorer (IBEX) has now operated in space for 7 years and returned nearly continuous observations that have led to scientific discoveries and reshaped our entire understanding of the outer heliosphere and its interaction with the local interstellar medium. Here we extend prior work, adding the 2014-2015 data for the first time, and examine, validate, initially analyze, and provide a complete 7-year set of Energetic Neutral Atom (ENA) observations from ~0.1 to 6 keV. The data, maps, and documentation provided here represent the 10th major release of IBEX data and include improvements to various prior corrections to provide the citable reference for the current version of IBEX data. We are now able to study time variations in the outer heliosphere and interstellar interaction over more than half a solar cycle. We find that the Ribbon has evolved differently than the globally distributed flux (GDF), with a leveling off and partial recovery of ENAs from the GDF, owing to solar wind output flattening and recovery. The Ribbon has now also lost its latitudinal ordering, which reflects the breakdown of solar minimum solar wind conditions and exhibits a greater time delay than for the surrounding GDF. Together, the IBEX observations strongly support a secondary ENA source for the Ribbon, and we suggest that this be adopted as the nominal explanation of the Ribbon going forward.