Investigating the IBEX Ribbon Structure a Solar Cycle Apart

Abstract A “Ribbon” of enhanced energetic neutral atom (ENA) emissions was discovered by the Interstellar Boundary Explorer in 2009, redefining our understanding heliosphere boundaries and physical processes occurring at interstellar interface. The Ribbon signal is intertwined with that a globally distributed flux (GDF) spans entire sky. To certain extent, separation methods enabled examining its evolution independent underlying GDF. Observations over full solar cycle revealed Ribbon’s evolving nature, intensity variations closely tracking those wind (SW) structure after few years delay, accounting for SW–ENA recycling process. In this work, we examine structure, namely ENA fluxes, angular width, circularity properties two years, 2009 2019, representative declining phases adjacent cycles. We find that, (i) fluxes have recovered nose direction south it down to ∼25° (for energies below 1.7 keV) not mid high ecliptic latitudes; (ii) width exhibits significant variability as function azimuthal angle; (iii) analysis suggests 2019 statistically consistent radius 2009. partial recovery aligned consensus closest point being southward region. large azimuth compared likely indicative small-scale within Ribbon.