The “IBEX Ribbon” as seen from an Interstellar Probe

Abstract:

The “IBEX Ribbon” is a region of enhanced Energetic Neutral Atom (ENA) emission, presumably in the outer heliosphere, located approximately where the radial direction is perpendicular to draped interstellar magnetic field. The ribbon is approximately circular (but not a great circle) in the sky. This feature was not anticipated before it was observed by the IBEX mission, and although there are strong candidates for the mechanism of its production, consensus has not been reached on the source mechanism of the observed emission. The IMAP mission will greatly improve our observations of this feature from the 1 AU vantage point, though ambiguities, e.g., its distance from the sun, thickness and other characteristics, will likely remain. An Interstellar Probe would provide us with the ability to resolve these ambiguities. In this work, we show simulated ENA images for different mechanisms and trajectories that could be taken from an ISP. Some mechanisms can be resolved effectively by the time the spacecraft reaches 10s of AU from the sun, while other characteristics can be imaged effectively and unambiguously as the spacecraft continues through the heliopause. Furthermore, and of similar importance, will be the ability to sample then plasma in the ribbon regions using in situ instrumentation. The candidate mechanisms for ribbon production require refinement of our understanding of the plasma physics of the region, and the questions raised thereby can best be resolved by direct measurements from an Interstellar Probe mission.