The energy-dependent position of the IBEX ribbon due to the solar wind structure

Abstract

Observations of energetic neutral atoms (ENAs) allow for remote studies of the plasma condition in the heliosphere and the neighboring local interstellar medium. The first IBEX results revealed an arc-like enhancement of the ENA intensity in the sky, known as the ribbon. The ribbon was not expected from the heliospheric models prior to the IBEX launch. One of the proposed explanations of the ribbon is the mechanism of the secondary ENA emission. The ribbon reveals energy-dependent structure in the relative intensity along its circumference and in the position. Namely, the ribbon geometric center varies systematically by about 10${}^{\circ }$ in the energy range 0.7-4.3 keV. Here, we show by analytic modeling that this effect is a consequence of the helio-latitudinal structure of the solar wind reflected in the secondary ENAs. Along with a recently measured distance to the ribbon source just beyond the heliopause, our findings support the connection of the ribbon with the local interstellar magnetic field by the mechanism of the secondary ENA emission. However, the magnitude of the center shift in the highest IBEX energy channel is much larger in the observations than expected from the modeling. This may be due to another, not currently recognized, process of ENA generation.

14 pages, 8 figures, 1 table, v3: corrected caption to Figure 3

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Cited by in corpus (9)

• Seven Years of Imaging the Global Heliosphere with IBEX
• Sun-Heliosphere Observation-based Ionization Rates Model
• The helium Warm Breeze in IBEX observations as a result of charge exchange collisions in the outer heliosheath
• Thermodynamics of the inner heliosheath
• Helium Energetic Neutral Atoms from the Heliosphere: Perspectives for Future Observations
• Modeling Emission of Heavy Energetic Neutral Atoms from the Heliosphere
• Investigating the IBEX Ribbon Structure a Solar Cycle Apart
• Spherical Harmonic Representation of Energetic Neutral Atom Flux Components Observed by IBEX
• Energetic neutral atoms from the heliosheath as an additional population of neutral hydrogen in the inner heliosphere