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

F. Allegrini; M. A. Dayeh; M. I. Desai; H. O. Funsten; S. A. Fuselier; P. H. Janzen; D. J. McComas; E. Möbius; D. B. Reisenfeld; D. F. Rodríguez M.; N. Schwadron; P. Wurz

doi:10.1016/j.pss.2013.06.014

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

F. Allegrini
, M. A. Dayeh
, M. I. Desai
, H. O. Funsten
, S. A. Fuselier
, P. H. Janzen
, D. J. McComas
, E. Möbius
, D. B. Reisenfeld
, D. F. Rodríguez M.
, N. Schwadron
, P. Wurz

Physics and Astronomy

Research output: Contribution to journal › Article › peer-review

32 Scopus citations

Abstract

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.

Original language	English
Pages (from-to)	232-242
Number of pages	11
Journal	Planetary and Space Science
Volume	85
DOIs	https://doi.org/10.1016/j.pss.2013.06.014
State	Published - Sep 1 2013

Funding

We acknowledge the use of ACE and Wind solar wind data, provided through the OMNIWeb Plus data at Goddard Space Flight Center through their public through their public interface. Simulation results have been provided by the Community Coordinated Modeling Center at Goddard Space Flight Center through their public Runs on Request system ( http://ccmc.gsfc.nasa.gov ). The CCMC is a multi-agency partnership between NASA, AFMC, AFOSR, AFRL, AFWA, NOAA, NSF and ONR. The BATSRUS Model was developed by the Dr. Tamas Gombosi et al. at the Center for Space Environment Modeling, University of Michigan. We also acknowledge the use of a Clementine basemap V2 map obtained from NASA PDS Imaging Node, USGS Astrogeology Research Program. D.F.R.M. and P.W. acknowledge the financial support by the Swiss national Science Foundation .

Funder number
147056

Keywords

ENA
Energetic neutral atoms
IBEX
Moon albedo
Solar wind

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10.1016/j.pss.2013.06.014

Cite this

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., Rodríguez M., D. F., Schwadron, N., & Wurz, P. (2013). Lunar energetic neutral atom (ENA) spectra measured by the interstellar boundary explorer (IBEX). Planetary and Space Science, 85, 232-242. https://doi.org/10.1016/j.pss.2013.06.014

@article{ac5c9c72ed2c42ad9bbeaffc8c64d622,

title = "Lunar energetic neutral atom (ENA) spectra measured by the interstellar boundary explorer (IBEX)",

abstract = "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 \textasciitilde{}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.",

keywords = "ENA, Energetic neutral atoms, IBEX, Moon albedo, Solar wind",

author = "F. Allegrini and Dayeh, \{M. A.\} and Desai, \{M. I.\} and Funsten, \{H. O.\} and Fuselier, \{S. A.\} and Janzen, \{P. H.\} and McComas, \{D. J.\} and E. M{\"o}bius and Reisenfeld, \{D. B.\} and \{Rodr{\'i}guez M.\}, \{D. F.\} and N. Schwadron and P. Wurz",

note = "Funding Information: We acknowledge the use of ACE and Wind solar wind data, provided through the OMNIWeb Plus data at Goddard Space Flight Center through their public through their public interface. Simulation results have been provided by the Community Coordinated Modeling Center at Goddard Space Flight Center through their public Runs on Request system ( http://ccmc.gsfc.nasa.gov ). The CCMC is a multi-agency partnership between NASA, AFMC, AFOSR, AFRL, AFWA, NOAA, NSF and ONR. The BATSRUS Model was developed by the Dr. Tamas Gombosi et al. at the Center for Space Environment Modeling, University of Michigan. We also acknowledge the use of a Clementine basemap V2 map obtained from NASA PDS Imaging Node, USGS Astrogeology Research Program. D.F.R.M. and P.W. acknowledge the financial support by the Swiss national Science Foundation .",

year = "2013",

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doi = "10.1016/j.pss.2013.06.014",

language = "English",

volume = "85",

pages = "232--242",

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T1 - Lunar energetic neutral atom (ENA) spectra measured by the interstellar boundary explorer (IBEX)

AU - Allegrini, F.

AU - Dayeh, M. A.

AU - Desai, M. I.

AU - Funsten, H. O.

AU - Fuselier, S. A.

AU - Janzen, P. H.

AU - McComas, D. J.

AU - Möbius, E.

AU - Reisenfeld, D. B.

AU - Rodríguez M., D. F.

AU - Schwadron, N.

AU - Wurz, P.

N1 - Funding Information: We acknowledge the use of ACE and Wind solar wind data, provided through the OMNIWeb Plus data at Goddard Space Flight Center through their public through their public interface. Simulation results have been provided by the Community Coordinated Modeling Center at Goddard Space Flight Center through their public Runs on Request system ( http://ccmc.gsfc.nasa.gov ). The CCMC is a multi-agency partnership between NASA, AFMC, AFOSR, AFRL, AFWA, NOAA, NSF and ONR. The BATSRUS Model was developed by the Dr. Tamas Gombosi et al. at the Center for Space Environment Modeling, University of Michigan. We also acknowledge the use of a Clementine basemap V2 map obtained from NASA PDS Imaging Node, USGS Astrogeology Research Program. D.F.R.M. and P.W. acknowledge the financial support by the Swiss national Science Foundation .

PY - 2013/9/1

Y1 - 2013/9/1

N2 - 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.

AB - 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.

KW - ENA

KW - Energetic neutral atoms

KW - IBEX

KW - Moon albedo

KW - Solar wind

UR - https://www.scopus.com/pages/publications/84883132811

U2 - 10.1016/j.pss.2013.06.014

DO - 10.1016/j.pss.2013.06.014

M3 - Article

AN - SCOPUS:84883132811

SN - 0032-0633

VL - 85

SP - 232

EP - 242

JO - Planetary and Space Science

JF - Planetary and Space Science

ER -

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

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Keywords

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