Lunar energetic neutral atom (ENA) spectra measured by the interstellar boundary explorer (IBEX)

Allegrini, F.; Dayeh, M.A.; Desai, M.I.; Funsten, H.O.; Fuselier, S.A.; Janzen, P.H.; McComas, D.J.; Möbius, E.; Reisenfeld, D.B.; Rodriguez Moreno, Diego Francisco; Schwadron, N.; Wurz, Peter (2013). Lunar energetic neutral atom (ENA) spectra measured by the interstellar boundary explorer (IBEX). Planetary and space science, 85, pp. 232-242. Elsevier 10.1016/j.pss.2013.06.014

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The solar wind continuously flows out from the Sun, filling interplanetary space and directly interacting with the surfaces of small planetary bodies and other objects throughout the solar system. A significant fraction of these ions backscatter from the surface as energetic neutral atoms (ENAs). The first observations of these ENA emissions from the Moon were recently reported from the Interstellar Boundary Explorer (IBEX). These observations yielded a lunar ENA albedo of ˜10% and showed that the Moon reflects ˜150 metric tons of neutral hydrogen per year. More recently, a survey of the first 2.5 years of IBEX observations of lunar ENAs was conducted for times when the Moon was in the solar wind. Here, we present the first IBEX ENA observations when the Moon is inside the terrestrial magnetosheath and compare them with observations when the Moon is in the solar wind. Our analysis shows that: (1) the ENA intensities are on average higher when the Moon is in the magnetosheath, (2) the energy spectra are similar above ~0.6* solar wind energy but below there are large differences of the order of a factor of 10, (3) the energy spectra resemble a power law with a "hump" at ˜0.6 * solar wind energy, and (4) this "hump" is broader when the Moon is in the magnetosheath. We explore potential scenarios to explain the differences, namely the effects of the topography of the lunar surface and the consequences of a very different Mach number in the solar wind versus in the magnetosheath.

Item Type:	Journal Article (Original Article)
Division/Institute:	08 Faculty of Science > Physics Institute > Space Research and Planetary Sciences
UniBE Contributor:	Rodriguez Moreno, Diego Francisco, Wurz, Peter
Subjects:	500 Science > 520 Astronomy 600 Technology > 620 Engineering 500 Science > 530 Physics
ISSN:	0032-0633
Publisher:	Elsevier
Language:	English
Submitter:	Cléa Serpollier
Date Deposited:	10 Jul 2014 16:40
Last Modified:	05 Dec 2022 14:29
Publisher DOI:	10.1016/j.pss.2013.06.014
URI:	https://boris.unibe.ch/id/eprint/44299