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| Titel |
Modeling the solar wind proton velocity space distribution function in the near lunar wake |
| VerfasserIn |
Shahab Fatemi, Mats Holmström, Yoshifumi Futaana |
| Konferenz |
EGU General Assembly 2011
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| Medientyp |
Artikel
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| Sprache |
Englisch
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| Digitales Dokument |
PDF |
| Erschienen |
In: GRA - Volume 13 (2011) |
| Datensatznummer |
250046014
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| Zusammenfassung |
| Solar wind proton fluxes have been observed close to the Moon in the lunar wake. In this
study, we investigate how these solar wind protons can access the lunar wake by using a 3D
hybrid model of plasma (particle ions and fluid electrons). However, since the protons
density at the lunar night side is several order of magnitudes less than that of the
solar wind, the number of particles in a hybrid model is too small to examine the
proton kinetics there. To improve the statistics, a Backward Liouville method is
used, where the electric and magnetic fields of the interaction region are obtained
from the hybrid simulation results, and ion trajectories are computed backward in
time from the location of interest using these fields. This allows us to study the
proton velocity space distribution function at the lunar night side in detail, and to
compare our modeling results with the observations performed with the SARA
(Sub-keV Atom Reflection Analyzer) instrument on-board Chandrayaan-1, which
observed proton fluxes in the lunar wake, ~50- behind the terminator in the equatorial
plane of the Moon, and at a height of 100 km [Futaana Y. et al., 2010, Journal of
Geophysical Research, Vol. 115, A10248]. It is shown that our model can explain the
reported observation of higher energy and lower density than predicted by 1-D
gas-dynamic theory, if we assume an anisotropic solar wind velocity space distribution
function. In addition, the absorption effect of the lunar surface on the solar wind
proton energy, density and velocity space distribution function in the lunar wake are
discussed. |
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