Interstellar Neutral Helium in the Heliosphere from IBEX Observations. V. Observations in IBEX-Lo ESA Steps 1, 2, and 3

Swaczyna, Paweł; Bzowski, Maciej; Kubiak, Marzena A.; Sokół, Justyna M.; Fuselier, Stephen A.; Galli, André; Heirtzler, David; Kucharek, Harald; McComas, David J.; Möbius, Eberhard; Schwadron, Nathan A.; Wurz, Peter (2018). Interstellar Neutral Helium in the Heliosphere from IBEX Observations. V. Observations in IBEX-Lo ESA Steps 1, 2, and 3. Astrophysical journal, 854(2), p. 119. Institute of Physics Publishing IOP 10.3847/1538-4357/aaabbf

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Direct-sampling observations of interstellar neutral (ISN) He by the Interstellar Boundary Explorer (IBEX) provide valuable insight into the physical state of and processes operating in the interstellar medium ahead of the heliosphere. The ISN He atom signals are observed at the four lowest ESA steps of the IBEX-Lo sensor. The observed signal is a mixture of the primary and secondary components of ISN He and H. Previously, only data from one of the ESA steps have been used. Here, we extend the analysis to data collected in the three lowest ESA steps with the strongest ISN He signal, for the observation seasons 2009–2015. The instrument sensitivity is modeled as a linear function of the atom impact speed onto the sensor’s conversion surface separately for each ESA step of the instrument. We find that the sensitivity increases from lower to higher ESA steps, but within each of the ESA steps it is a decreasing function of the atom impact speed. This result may be influenced by the hydrogen contribution, which was not included in the adopted model, but seems to exist in the signal. We conclude that the currently accepted temperature of ISN He and velocity of the Sun through the interstellar medium do not need a revision, and we sketch a plan of further data analysis aiming at investigating ISN H and a better understanding of the population of ISN He originating in the outer heliosheath.

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:

04 Apr 2018 13:07

Last Modified:

29 May 2019 18:03

Publisher DOI:

10.3847/1538-4357/aaabbf

BORIS DOI:

10.7892/boris.112886

URI:

https://boris.unibe.ch/id/eprint/112886

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