Local Interstellar Neutral Hydrogen sampled in-situ by IBEX

Abstract

Hydrogen gas is the dominant component of the local interstellar medium. However, due to ionization and interaction with the heliosphere, direct sampling of neutral hydrogen in the inner heliosphere is more difficult than sampling the local interstellar neutral helium, which penetrates deep into the heliosphere. In this paper we report on the first detailed analysis of the direct sampling of neutral hydrogen from the local interstellar medium. We confirm that the arrival direction of hydrogen is offset from that of the local Helium component. We further report the discovery of a variation of the penetrating Hydrogen over the first two years of IBEX observations. Observations are consistent with hydrogen experiencing an effective ratio of outward solar radiation pressure to inward gravitational force greater than unity (μ>1); the temporal change observed in the local interstellar hydrogen flux can be explained with solar variability.

References in corpus (7)

• The Structure of the Local Interstellar Medium V: Electron Densities
• Survival probability and energy modification of hydrogen Energetic Neutral Atoms on their way from the termination shock to Earth orbit
• Density of neutral interstellar hydrogen at the termination shock from Ulysses pickup ion observations
• Heliospheric Response to Different Possible Interstellar Environments
• The Velocity Distribution of the Nearest Interstellar Gas
• Effects of interstellar and solar wind ionized helium on the interaction of the solar wind with the local interstellar medium
• Can IBEX Identify Variations in the Galactic Environment of the Sun using Energetic Neutral Atom (ENAs)?

Cited by in corpus (22)

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• Modulation of neutral interstellar He, Ne, O in the heliosphere. Survival probabilities and abundances at IBEX
• The helium Warm Breeze in IBEX observations as a result of charge exchange collisions in the outer heliosheath
• Interstellar Neutral Helium in the Heliosphere from IBEX Observations. I. Uncertainties and Backgrounds in the Data and Parameter Determination Method
• Interstellar neutral helium in the heliosphere from IBEX observations. V. Observations in IBEX-Lo ESA steps 1, 2, & 3
• Very Local Interstellar Medium Revealed by Complete Solar Cycle of Interstellar Neutral Helium Observations with IBEX
• The Interstellar Neutral He haze in the heliosphere: what can we learn?
• Interstellar hydrogen fluxes measured by IBEX-Lo in 2009: numerical modeling and comparison with the data
• Evolution of the solar Ly-$\alpha$ line profile during the solar cycle. II. How accurate is the present radiation pressure paradigm for interstellar neutral H in the heliosphere?
• Update of the Solar Lyman-Alpha Profile Line Model
• Precision Pointing of IBEX-Lo Observations
• Neutral interstellar helium parameters based on Ulysses/GAS and IBEX-Lo observations: what are the reasons for the differences?
• Interstellar Conditions Deduced from Interstellar Neutral Helium Observed by IBEX and Global Heliosphere Modeling
• Angular Scattering in Charge Exchange: Issues and Implications for Secondary Interstellar Hydrogen
• Science Opportunities from Observations of the Interstellar Neutral Gas with Adjustable Boresight Direction
• Assessment of detectability of neutral interstellar deuterium by IBEX observations
• Relative In-flight Response of IBEX-Lo to Interstellar Neutral Helium Atoms
• An empirical model of Energetic Neutral Atom imaging of the heliosphere and its implications for future heliospheric missions at great heliocentric distances
• Energetic neutral atoms from the heliosheath as an additional population of neutral hydrogen in the inner heliosphere