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Scattering characteristics and imaging of energetic neutral atoms from the Moon in the terrestrial magnetosheath
Barabash, Stas; Futaana, Yoshifumi; Wieser, Martin +6 more
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…
A family for miniature, easily reconfigurable particle sensors for space plasma measurements
Barabash, S.; Wieser, M.
Over the last 15 years the Swedish Institute of Space Physics developed a line of miniaturized ion mass analyzers for space plasma studies with masses of 400-600 g and highly compact and dense design to minimize the volume. The sensors cover an energy range from few eV up to 15 keV and reach an angular coverage up to hemispherical and mass resolut…
First direct observation of sputtered lunar oxygen
Barabash, S.; Holmström, M.; Futaana, Y. +5 more
We present the first direct measurement of neutral oxygen in the lunar exosphere, detected by the Chandrayaan-1 Energetic Neutral Analyzer (CENA). With the lunar surface consisting of about 60% of oxygen in number, the neutral oxygen detected in CENA's energy range (11 eV-3.3 keV) is attributed to have originated from the lunar surface, where it w…
Backscattered energetic neutral atoms from the Moon in the Earth's plasma sheet observed by Chandarayaan-1/Sub-keV Atom Reflecting Analyzer instrument
Barabash, Stas; Futaana, Yoshifumi; Wieser, Martin +8 more
We present the observations of energetic neutral atoms (ENAs) produced at the lunar surface in the Earth's magnetotail. When the Moon was located in the terrestrial plasma sheet, Chandrayaan-1 Energetic Neutrals Analyzer (CENA) detected hydrogen ENAs from the Moon. Analysis of the data from CENA together with the Solar Wind Monitor (SWIM) onboard …
Energetic neutral atom imaging of the lunar surface
Barabash, S.; Holmström, M.; Futaana, Y. +7 more
Since the Moon is not shielded by a global magnetic field or by an atmosphere, solar wind plasma impinges onto the lunar surface almost unhindered. Until recently, it was assumed that almost all of the impinging solar wind ions are absorbed by the surface. However, recent Interstellar Boundary Explorer, Chandrayaan-1, and Kaguya observations showe…
Near-lunar proton velocity distribution explained by electrostatic acceleration
Hutchinson, I. H.
The observation of parallel ion velocity in the near-lunar wake approximately equal to external solar wind velocity can be explained within uncertainties by an analytic electrostatic expansion model. The one-dimensional model frequently used is inadequate because it does not account for the moon's spherical shape. However, application of a more re…
Energetic neutral atom observations of magnetic anomalies on the lunar surface
Barabash, S.; Holmström, M.; Futaana, Y. +5 more
SARA, the Sub-KeV Atom Analyzer, on board Chandrayaan-1 recorded the first image of a minimagnetosphere above a lunar magnetic anomaly using energetic neutral atoms (ENAs). It was shown that this magnetosphere, which is located near the Gerasimovich crater, is able to reduce the solar wind ion flux impinging onto the lunar surface by more than 50%…
Dynamics of solar wind protons reflected by the Moon
Barabash, S.; Holmström, M.; Futaana, Y. +2 more
Solar system bodies that lack a significant atmosphere and significant internal magnetic fields, such as the Moon and asteroids, have been considered passive absorbers of the solar wind. However, ion observations near the Moon by the SELENE spacecraft show that a fraction of the impacting solar wind protons are reflected by the surface of the Moon…
Protons in the near-lunar wake observed by the Sub-keV Atom Reflection Analyzer on board Chandrayaan-1
Barabash, S.; Holmström, M.; Futaana, Y. +7 more
Significant proton fluxes were detected in the near-wake region of the Moon by an ion mass spectrometer on board Chandrayaan-1. The energy of these nightside protons is slightly higher than the energy of the solar wind protons. The protons are detected close to the lunar equatorial plane at a 140° solar zenith angle, that is, ∼50° behind the termi…