HR: 0800h
AN: SH51B-0273    [Abstracts]
TI: Low Energetic Neutral Atom (LENA) imaging of the Moon
AU: * Futaana, Y
EM: futaana@irf.se
AF: Swedish Institute of Space Physics, Box812, Kiruna, 98128 Sweden
AU: Barabash, S
EM: stas@irf.se
AF: Swedish Institute of Space Physics, Box812, Kiruna, 98128 Sweden
AU: Holmstr\"om, M
EM: matsh@irf.se
AF: Swedish Institute of Space Physics, Box812, Kiruna, 98128 Sweden
AU: Bhardwaj, A
EM: Anil.Bhardwaj@msfc.nasa.gov
AF: NASA-MSFC, NSSTC/SD50, 320 Sparkman Drive, Huntsville, AL 35805 United States
AB: Since the Moon possesses neither global magnetic field nor atmosphere, the solar wind can directly precipitate on its surface causing atomic sputtering. The sputtered low energetic neutral atoms(LENAs) can be used to image the precipitation area and characterize the sputtering process remotely. Imaging the sputtered LENAs with sufficiently high mass resolution reveals (1) the moon surface elemental composition, (2) the solar wind surface interaction pattern, and (3) one of the most significant sources of the Moon's exosphere. The relative yield of different elements reflects the surface elemental composition, then the LENA images can be converted to the surface composition maps. The Lunar surface magnetic anomalies could stand off the solar wind locally. The solar wind flux cannot reach the surface in these areas and hence the LENA flux disappears. We have calculated the LENA flux from sunlit hemisphere, which reveals that the anomalous field can be clearly seen on LENA images. The strength of the magnetic anomaly can also be estimated from the shape of the ENA flux voids on the image by assuming the pressure balance condition. Since the solar wind is a supersonic flow and has a finite thermal velocity, it can also reach areas not accessible by solar photons such as permanently shadowed craters and areas beyond the limb. We have calculated expected sputtered LENA flux from the dark side of the moon in two different models. We first treated the solar wind flow into the shadowed region parallel to the magnetic field considering the ambipolar diffusion. We then considered the finite-gyroradius effect of individual solar wind protons by using the particle concept. The calculation revealed that the sputtered ENAs can be imaged and will provide valuable information on the unlit region.
DE: 7837 Neutral particles
DE: 5462 Polar regions
DE: 5709 Composition
DE: 5794 Instruments and techniques
DE: 2756 Planetary magnetospheres (5443, 5737, 6030)
SC: SPA-Solar and Heliospheric Physics [SH]
MN: 2004 AGU Fall Meeting