Scattering characteristics and imaging of energetic neutral atoms from the Moon in the terrestrial magnetosheath

Lue, Charles; Futaana, Yoshifumi; Barabash, Stas; Saito, Yoshifumi; Nishino, Masaki; Wieser, Martin; Asamura, Kazushi; Bhardwaj, Anil; Wurz, Peter (2016). Scattering characteristics and imaging of energetic neutral atoms from the Moon in the terrestrial magnetosheath. Journal of Geophysical Research: Space Physics, 121(1), pp. 432-445. AGU Publications 10.1002/2015ja021826

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We study hydrogen energetic neutral atom (ENA) emissions from the lunar surface, when the Moon is inside the terrestrial magnetosheath. The ENAs are generated by neutralization and backscattering of incident protons of solar wind origin. First, we model the effect of the increased ion temperature in the magnetosheath (>10 times larger than that in the undisturbed solar wind) on the ENA scattering characteristics. Then, we apply these models to ENA measurements by Chandrayaan-1 and simultaneous ion measurements by Kaguya at the Moon, in the magnetosheath. We produce maps of the ENA scattering fraction, covering a region at the lunar near-side that includes mare and highland surfaces and several lunar magnetic anomalies. We see clear signatures of plasma shielding by the magnetic anomalies. The maps are made at different lunar local times, and the results indicate an extended influence and altered morphology of the magnetic anomalies at shallower incidence angles of the magnetosheath protons. The scattering fraction from the unmagnetized regions remains consistent with that in the undisturbed solar wind (10%-20%). Moreover, the observed ENA energy spectra are well reproduced by our temperature-dependent model. We conclude that the ENA scattering process is unchanged in the magnetosheath. Similarly to the undisturbed solar wind case, it is only magnetic anomalies that provide contrast in the ENA maps, not any selenomorphological features such as mare and highland regions.

Item Type:

Journal Article (Original Article)

Division/Institute:

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

UniBE Contributor:

Wieser, Martin and Wurz, Peter

Subjects:

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

ISSN:

2169-9380

Publisher:

AGU Publications

Language:

English

Submitter:

Katharina Weyeneth-Moser

Date Deposited:

11 Nov 2016 17:10

Last Modified:

11 Nov 2016 17:10

Publisher DOI:

10.1002/2015ja021826

BORIS DOI:

10.7892/boris.89508

URI:

https://boris.unibe.ch/id/eprint/89508

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