Swaczyna, P.; Bzowski, M.; Heerikhuisen, J.; Kubiak, M. A.; Rahmanifard, F.; Zirnstein, E. J.; Fuselier, S. A.; Galli, A.; McComas, D. J.; Möbius, E.; Schwadron, N. A. (2023). Interstellar Conditions Deduced from Interstellar Neutral Helium Observed by IBEX and Global Heliosphere Modeling. Astrophysical journal, 953(1), p. 107. Institute of Physics Publishing IOP 10.3847/1538-4357/ace719
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In situ observations of interstellar neutral (ISN) helium atoms by the IBEX-Lo instrument on board the Interstellar Boundary Explorer (IBEX) mission are used to determine the velocity and temperature of the pristine very local interstellar medium (VLISM). Most ISN helium atoms penetrating the heliosphere, known as the primary population, originate in the pristine VLISM. As the primary atoms travel through the outer heliosheath, they charge exchange with He+ ions in slowed and compressed plasma, creating the secondary population. With more than 2.4 million ISN helium atoms being sampled by IBEX during ISN seasons 2009–2020, we compare the observations with the predictions of a parameterized model of ISN helium transport in the heliosphere. We account for the filtration of ISN helium atoms at the heliospheric boundaries by charge-exchange and elastic collisions. We examine the sensitivity of the ISN helium fluxes to the interstellar conditions described by the pristine VLISM velocity, temperature, magnetic field, and composition. We show that comprehensive modeling of the filtration processes is critical for interpreting ISN helium observations, as the change in the derived VLISM conditions exceeds the statistical uncertainties when accounting for these effects. The pristine VLISM parameters found by this analysis are the flow speed (26.6 km s−1), inflow direction in ecliptic coordinates (255fdg7, 5fdg04), temperature (7350 K), and B − V plane inclination to the ecliptic plane (53fdg7). The derived pristine VLISM He+ density is 9.7 × 10−3 cm−3. Additionally, we show a strong correlation between the interstellar plasma density and magnetic field strength deduced from these observations.
Item Type: |
Journal Article (Original Article) |
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Division/Institute: |
08 Faculty of Science > Physics Institute > Space Research and Planetary Sciences 08 Faculty of Science > Physics Institute |
UniBE Contributor: |
Galli, A |
Subjects: |
500 Science > 530 Physics 500 Science > 520 Astronomy 600 Technology > 620 Engineering |
ISSN: |
0004-637X |
Publisher: |
Institute of Physics Publishing IOP |
Language: |
English |
Submitter: |
Dora Ursula Zimmerer |
Date Deposited: |
12 Feb 2024 14:03 |
Last Modified: |
12 Feb 2024 14:03 |
Publisher DOI: |
10.3847/1538-4357/ace719 |
BORIS DOI: |
10.48350/192802 |
URI: |
https://boris.unibe.ch/id/eprint/192802 |
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