Interstellar Neutral Helium in the Heliosphere from IBEX Observations. VI. The He + Density and the Ionization State in the Very Local Interstellar Matter

Bzowski, M.; Czechowski, A.; Frisch, P. C.; Fuselier, S. A.; Galli, André; Grygorczuk, J.; Heerikhuisen, J.; Kubiak, M. A.; Kucharek, H.; McComas, D. J.; Möbius, E.; Schwadron, N. A.; Slavin, J.; Sokół, J. M.; Swaczyna, P.; Wurz, Peter; Zirnstein, E. J. (2019). Interstellar Neutral Helium in the Heliosphere from IBEX Observations. VI. The He + Density and the Ionization State in the Very Local Interstellar Matter. Astrophysical journal, 882(1), p. 60. Institute of Physics Publishing IOP 10.3847/1538-4357/ab3462

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Interstellar neutral gas atoms penetrate the heliopause and reach 1 au, where they are detected by Interstellar Boundary Explorer (IBEX). The flow of neutral interstellar helium through the perturbed interstellar plasma in the outer heliosheath (OHS) results in the creation of a secondary population of interstellar He atoms, the so-called Warm Breeze, due to charge exchange with perturbed ions. The secondary population brings the imprint of the OHS conditions to the IBEX-Lo instrument. Based on a global simulation of the heliosphere with measurementbased parameters and detailed kinetic simulation of the filtration of He in the OHS, we find the number density of the interstellar He+ population to be (8.98±0.12)×10−3 cm−3. With this, we obtain the absolute density of interstellar H+ as 5.4×10−2 cm−3 and that of electrons as 6.3×10−2 cm−3, with ionization degrees of 0.26 for H and 0.37 for He. The results agree with estimates of the parameters of the Very Local Interstellar Matter obtained from fitting the observed spectra of diffuse interstellar EUV and the soft X-ray background.

Item Type:

Journal Article (Original Article)

Division/Institute:

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

UniBE Contributor:

Galli, André and Wurz, Peter

Subjects:

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

ISSN:

0004-637X

Publisher:

Institute of Physics Publishing IOP

Language:

English

Submitter:

Dora Ursula Zimmerer

Date Deposited:

25 Sep 2019 17:25

Last Modified:

23 Oct 2019 10:45

Publisher DOI:

10.3847/1538-4357/ab3462

BORIS DOI:

10.7892/boris.133459

URI:

https://boris.unibe.ch/id/eprint/133459

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