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

Bzowski, M.; Galli, André

doi:10.3847/1538-4357/aaf1b2

Cited by 2 publications

(2 citation statements)

References 40 publications

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“…In reality, some PUIs are lost to charge-exchange interactions with exospheric neutrals, energetic neutral hydrogen atoms (H ENAs), and ISN hydrogen atoms. According to Bzowski & Galli (2019), H ENAs density at 1 AU is ∼4e−4 cm −3 and lower than the ISN hydrogen density. 1.…”

Section: Interval Selections and Data Analysismentioning

confidence: 98%

Multipoint Density Measurements of Geocoronal Pickup Ions

Gomez

Fuselier

Sokół

et al. 2021

Geophysical Research Letters

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Observations of the plasma environment outside of the Earth's magnetosphere by the Magnetospheric Multiscale Mission Hot Plasma Composition Analyzers (MMS‐HPCAs) allow density measurements of geocoronal hydrogen pickup ions (PUIs). A study of this environment from December 4, 2019 to December 6, 2019, part of a single orbital period of the MMS spacecraft, revealed an inverse square dependence on PUI density. This dependence corresponds well with an inverse‐cube dependence on the neutral hydrogen density within the geocorona.

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Section: Interval Selections and Data Analysismentioning

confidence: 98%

Multipoint Density Measurements of Geocoronal Pickup Ions

Gomez

Fuselier

Sokół

et al. 2021

Geophysical Research Letters

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“…Furthermore, neutralized energetic ions, such as PUIs, form energetic neutral atoms (ENAs). Even though ENAs contribute to the neutral hydrogen density in the heliosphere, their density is orders of magnitude lower than that of the ISN hydrogen (Bzowski & Galli 2019). PUIs are also created through photoionization and electron impact ionization (Bzowski et al 2013).…”

Section: Introductionmentioning

confidence: 99%

Interstellar Neutral Hydrogen in the Heliosphere: New Horizons Observations in the Context of Models

Swaczyna,

Bzowski,

Dialynas

et al. 2024

ApJL

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Interstellar neutral (ISN) hydrogen is the most abundant species in the outer heliosheath and the very local interstellar medium (VLISM). Charge-exchange collisions in the outer heliosheath result in filtration, reducing the ISN hydrogen density inside the heliosphere. Additionally, these atoms are intensively ionized close to the Sun, resulting in a substantial reduction of their density within a few astronomical units from the Sun. The products of this ionization—pickup ions (PUIs)—are detected by charged particle detectors. The Solar Wind Around Pluto instrument on New Horizons provides, for the first time, PUI observations from the distant heliosphere. We analyze the observations collected between 22 and 52 au from the Sun to find the ISN hydrogen density profile and compare the results with predictions from global heliosphere models. We conclude that the density profile derived from the observations is inconsistent with steady-state model predictions. This discrepancy is not explained by time variations close to the Sun and thus may be related to the temporal evolution of the outer boundaries or VLISM conditions. Furthermore, we show that the cold and hot models of ISN hydrogen distribution are not a good approximation closer to the termination shock. Therefore, we recommend a new fiduciary point based on the available New Horizons observations at 40 au from the Sun, at ecliptic direction (285.°62, 1.°94), where the ISN hydrogen density is 0.11 cm−3. The continued operation of New Horizons should give better insight into the source of the discussed discrepancy.

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

Abstract: Interstellar neutral hydrogen (ISN H) gas penetrates freely the heliopause. Inside the inner heliosheath, the charge-exchange interaction of this gas with the shocked solar wind and pickup ions creates energetic neutral atoms (ENAs).

Cited by 2 publications

References 40 publications

Multipoint Density Measurements of Geocoronal Pickup Ions

Multipoint Density Measurements of Geocoronal Pickup Ions

Interstellar Neutral Hydrogen in the Heliosphere: New Horizons Observations in the Context of Models

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