Energetic Neutral Atoms from the Heliosheath as an Additional Population of Neutral Hydrogen in the Inner Heliosphere

Bzowski, M.; Galli, André (2019). Energetic Neutral Atoms from the Heliosheath as an Additional Population of Neutral Hydrogen in the Inner Heliosphere. Astrophysical journal, 870(2), pp. 1-8. Institute of Physics Publishing IOP 10.3847/1538-4357/aaf1b2

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Interstellar neutral hydrogen (ISN H) gas penetrates freely the heliopause. Inside the inner heliosheath, the chargeexchange interaction of this gas with the shocked solar wind and pickup ions creates energetic neutral atoms (ENAs). ISN H is strongly depleted inside the termination shock but a fraction reaches the Earth’s orbit. In these regions of the heliosphere, ISN H is the source population for interstellar pickup ions and for the heliospheric backscatter glow. The globally distributed flux (GDF) of ENAs created in the inner heliosheath has been sampled directly by the Interstellar Boundary Explorer. Based on these measurements, we calculate the density of the GDF ENA population at the Earth’s orbit. We find that this number density is between 10⁻⁴ and 10⁻³ cm⁻³, i.e., comparable in magnitude to the number density of ISN H in the downwind portion of the Earth’s orbit. Half of this atom population has energies less than ~80 eV. This GDF population of neutral hydrogen is likely to provide a significant contribution to the intensity of heliospheric glow in the downwind hemisphere, may be the source of the inner source of hydrogen pickup ions, and may be responsible for the excess of production of pickup ions found in the analysis of magnetic wave events induced by the proton pickup process in the downwind region at 1 au from the Sun.

Item Type:

Journal Article (Original Article)


08 Faculty of Science > Physics Institute > Space Research and Planetary Sciences
08 Faculty of Science > Physics Institute

UniBE Contributor:

Galli, André


500 Science > 520 Astronomy
600 Technology > 620 Engineering
500 Science > 530 Physics




Institute of Physics Publishing IOP




Dora Ursula Zimmerer

Date Deposited:

22 Jul 2019 11:00

Last Modified:

22 Oct 2019 16:30

Publisher DOI:






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