Helium Energetic Neutral Atoms from the Heliosphere: Perspectives for Future Observations

Abstract

Observations of energetic neutral atoms (ENAs) allow for remote sensing of plasma properties in distant regions of the heliosphere. So far, most of the observations have concerned only hydrogen atoms. In this paper, we present perspectives for observations of helium energetic neutral atoms (He ENAs). We calculated the expected intensities of He ENAs created by the neutralization of helium ions in the inner heliosheath and through the secondary ENA mechanism in the outer heliosheath. We found that the dominant source region for He ENAs is the inner heliosheath. The obtained magnitudes of intensity spectra suggest that He ENAs can be observed with future ENA detectors, as those planned on Interstellar Mapping and Acceleration Probe. Observing He ENAs is most likely for energies from a few to a few tens of keV/nuc. Estimates of the expected count rates show that the ratio of helium to hydrogen atoms registered in the detectors can be as low as 1:10^4. Consequently, the detectors need to be equipped with an appropriate mass spectrometer capability, allowing for recognition of chemical elements. Due to the long mean free paths of helium ions in the inner heliosheath, He ENAs are produced also in the distant heliospheric tail. This implies that observations of He ENAs can resolve its structure, which seems challenging from observations of hydrogen ENAs since energetic protons are neutralized before they progress deeper in the heliospheric tail.

31 pages, 12 figures, 3 tables, published in The Astrophysical Journal

References in corpus (6)

• The effects of a kappa-distribution in the heliosheath on the global heliosphere and ENA flux at 1 AU
• Warm Breeze from the starboard bow: a new population of neutral helium in the heliosphere
• Comparing various multi-component global heliosphere models
• Neutral H density at the termination shock: a consolidation of recent results
• Photoionization rates for helium: update
• Heliosphere for a wide range of interstellar magnetic field strengths as a source of energetic neutral atoms

Cited by in corpus (4)

• Modeling Emission of Heavy Energetic Neutral Atoms from the Heliosphere
• An empirical model of Energetic Neutral Atom imaging of the heliosphere and its implications for future heliospheric missions at great heliocentric distances
• Magnetohydrodynamic/Kinetic Modeling of the Interaction between the Solar Wind and the Local Interstellar Medium with He${}^{+}$, He${}^{2+}$, and Pickup H${}^{+}$ ions and H, He Atoms
• Production and Loss Processes of Hydrogen Energetic Neutral Atoms in the Heliosphere from 5 eV to 500 keV