15 yr of Interstellar Neutral Hydrogen Observed with the Interstellar Boundary Explorer

The interactions of our heliosphere with the surrounding local interstellar medium (LISM) lead to a range of observable phenomena such as energetic neutral atoms (ENAs) from the boundary regions of the heliosphere and the influx of interstellar neutrals (ISNs) into the inner solar system. Hydrogen i...

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Main Authors: André Galli, Paweł Swaczyna, Maciej Bzowski, Marzena A. Kubiak, Izabela Kowalska-Leszczynska, Peter Wurz, Fatemeh Rahmanifard, Nathan A. Schwadron, Eberhard Möbius, Stephen A. Fuselier, Justyna M. Sokół, Jonathan Gasser, Jacob Heerikhuisen, David J. McComas
Format: Article
Language:English
Published: IOP Publishing 2025-01-01
Series:The Astrophysical Journal Supplement Series
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Online Access:https://doi.org/10.3847/1538-4365/adc451
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author André Galli
Paweł Swaczyna
Maciej Bzowski
Marzena A. Kubiak
Izabela Kowalska-Leszczynska
Peter Wurz
Fatemeh Rahmanifard
Nathan A. Schwadron
Eberhard Möbius
Stephen A. Fuselier
Justyna M. Sokół
Jonathan Gasser
Jacob Heerikhuisen
David J. McComas
author_facet André Galli
Paweł Swaczyna
Maciej Bzowski
Marzena A. Kubiak
Izabela Kowalska-Leszczynska
Peter Wurz
Fatemeh Rahmanifard
Nathan A. Schwadron
Eberhard Möbius
Stephen A. Fuselier
Justyna M. Sokół
Jonathan Gasser
Jacob Heerikhuisen
David J. McComas
author_sort André Galli
collection DOAJ
description The interactions of our heliosphere with the surrounding local interstellar medium (LISM) lead to a range of observable phenomena such as energetic neutral atoms (ENAs) from the boundary regions of the heliosphere and the influx of interstellar neutrals (ISNs) into the inner solar system. Hydrogen is the dominant neutral species in the LISM, but due to ionization and radiation pressure, only a fraction of the ISN H atoms reach the inner solar system close to Earth. Monitoring this signal therefore provides observational constraints on our assumptions of the LISM and the solar-activity-dependent loss processes inside the heliosphere. The IBEX-Lo instrument on board the Interstellar Boundary Explorer has been the only instrument so far to measure ISN H atoms directly, together with ISN D, He, Ne, O, and ENAs in the energy range from tens of eV to 2 keV. This study covers 15 yr of IBEX-Lo ISN H observations, i.e., more than one solar cycle and includes two solar minima when the ISN H signal in IBEX-Lo is strongest. Despite the very intense ISN He signal, the ISN H signal can be retrieved with appropriate knowledge of the instrument, choice of optimum observation season, and supporting modeling. The retrieved ISN H signal shows a clear anticorrelation with solar activity. The resulting ISN H maps are available in orbit format and in ecliptic coordinates and will be the basis for future more detailed comparison with heliosphere models.
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spelling doaj-art-3fb4c58ea0194b93b88f0295294e4f222025-08-20T03:06:57ZengIOP PublishingThe Astrophysical Journal Supplement Series0067-00492025-01-012781110.3847/1538-4365/adc45115 yr of Interstellar Neutral Hydrogen Observed with the Interstellar Boundary ExplorerAndré Galli0https://orcid.org/0000-0003-2425-3793Paweł Swaczyna1https://orcid.org/0000-0002-9033-0809Maciej Bzowski2https://orcid.org/0000-0003-3957-2359Marzena A. Kubiak3https://orcid.org/0000-0002-5204-9645Izabela Kowalska-Leszczynska4https://orcid.org/0000-0002-6569-3800Peter Wurz5https://orcid.org/0000-0002-2603-1169Fatemeh Rahmanifard6https://orcid.org/0000-0001-9316-0553Nathan A. Schwadron7https://orcid.org/0000-0002-3737-9283Eberhard Möbius8Stephen A. Fuselier9https://orcid.org/0000-0003-4101-7901Justyna M. Sokół10https://orcid.org/0000-0002-4173-3601Jonathan Gasser11Jacob Heerikhuisen12https://orcid.org/0000-0001-7867-3633David J. McComas13https://orcid.org/0000-0001-6160-1158Space Science and Planetology, Physics Institute, University of Bern , Bern, Switzerland ; andre.galli@unibe.chSpace Research Centre PAS (CBK PAN) , Warsaw, PolandSpace Research Centre PAS (CBK PAN) , Warsaw, PolandSpace Research Centre PAS (CBK PAN) , Warsaw, PolandSpace Research Centre PAS (CBK PAN) , Warsaw, PolandSpace Science and Planetology, Physics Institute, University of Bern , Bern, Switzerland ; andre.galli@unibe.chUniversity of New Hampshire , Durham, NH, USAUniversity of New Hampshire , Durham, NH, USAUniversity of New Hampshire , Durham, NH, USASouthwest Research Institute , San Antonio, TX, USA; University of Texas at San Antonio , San Antonio, TX, USASouthwest Research Institute , San Antonio, TX, USASouthwest Research Institute , San Antonio, TX, USADepartment of Mathematics and Statistics, University of Waikato , Hamilton, New ZealandDepartment of Astrophysical Sciences, Princeton University , Princeton, NJ, USAThe interactions of our heliosphere with the surrounding local interstellar medium (LISM) lead to a range of observable phenomena such as energetic neutral atoms (ENAs) from the boundary regions of the heliosphere and the influx of interstellar neutrals (ISNs) into the inner solar system. Hydrogen is the dominant neutral species in the LISM, but due to ionization and radiation pressure, only a fraction of the ISN H atoms reach the inner solar system close to Earth. Monitoring this signal therefore provides observational constraints on our assumptions of the LISM and the solar-activity-dependent loss processes inside the heliosphere. The IBEX-Lo instrument on board the Interstellar Boundary Explorer has been the only instrument so far to measure ISN H atoms directly, together with ISN D, He, Ne, O, and ENAs in the energy range from tens of eV to 2 keV. This study covers 15 yr of IBEX-Lo ISN H observations, i.e., more than one solar cycle and includes two solar minima when the ISN H signal in IBEX-Lo is strongest. Despite the very intense ISN He signal, the ISN H signal can be retrieved with appropriate knowledge of the instrument, choice of optimum observation season, and supporting modeling. The retrieved ISN H signal shows a clear anticorrelation with solar activity. The resulting ISN H maps are available in orbit format and in ecliptic coordinates and will be the basis for future more detailed comparison with heliosphere models.https://doi.org/10.3847/1538-4365/adc451HeliosphereHeliosheathInterstellar mediumInterstellar atomic gasSolar cycle
spellingShingle André Galli
Paweł Swaczyna
Maciej Bzowski
Marzena A. Kubiak
Izabela Kowalska-Leszczynska
Peter Wurz
Fatemeh Rahmanifard
Nathan A. Schwadron
Eberhard Möbius
Stephen A. Fuselier
Justyna M. Sokół
Jonathan Gasser
Jacob Heerikhuisen
David J. McComas
15 yr of Interstellar Neutral Hydrogen Observed with the Interstellar Boundary Explorer
The Astrophysical Journal Supplement Series
Heliosphere
Heliosheath
Interstellar medium
Interstellar atomic gas
Solar cycle
title 15 yr of Interstellar Neutral Hydrogen Observed with the Interstellar Boundary Explorer
title_full 15 yr of Interstellar Neutral Hydrogen Observed with the Interstellar Boundary Explorer
title_fullStr 15 yr of Interstellar Neutral Hydrogen Observed with the Interstellar Boundary Explorer
title_full_unstemmed 15 yr of Interstellar Neutral Hydrogen Observed with the Interstellar Boundary Explorer
title_short 15 yr of Interstellar Neutral Hydrogen Observed with the Interstellar Boundary Explorer
title_sort 15 yr of interstellar neutral hydrogen observed with the interstellar boundary explorer
topic Heliosphere
Heliosheath
Interstellar medium
Interstellar atomic gas
Solar cycle
url https://doi.org/10.3847/1538-4365/adc451
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