DPS 35th Meeting, 1-6 September 2003
Session 23. Planetary Bookends I
Oral, Chairs: W. B. McKinnon and W. M. Grundy, Thursday, September 4, 2003, 10:30am-12:00noon, DeAnza I-II

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[23.09] Mercury's Sodium Exosphere: Magnetospheric Ion recycling

F. Leblanc (Service d'Aeronomie du CNRS), D. Delcourt (Centre d'Etude des Environnements Terrestre et Planetaires), R.E. Johnson, M. Liu (University of Virginia)

The temporal and spatial variability in 3D of Mercury's neutral sodium exosphere and its correlation with the sodium density in Mercury's surface was described for Mercury's motion around the Sun (Leblanc and Johnson 2003). Four processes for ejection of sodium were taken into account: thermal and photon stimulated desorptions, solar wind sputtering and micro-meteoroid vaporization. A model of ion circulation in Mercury's magnetosphere developed by Delcourt et al. (2002; 2003) is used here to follow the newly ionized particles produced by this model of Mercury's neutral sodium exosphere. The motion of Na+ and Na around Mercury are dynamically coupled. The contribution to sputtering and the local increase in the Na density in Mercury's surface by the reimpacting ions is discussed.

Magnetospheric ion sputtering does not contribute significantly to the total amount of Na atoms ejected into Mercury's exosphere because of the rather small flux of magnetospheric ion reimpacting Mercury's surface. However magnetospheric ion reimplantation in Mercury's surface is sufficiently concentrated inside narrow latitude bands to enhance significantly the local concentration of sodium in Mercury's surface. As a consequence, certain peaks in Mercury's exospheric sodium emission observed at high latitudes could be due to the release on the dayside of these magnetospheric sodium ions reimplanted into Mercury's nightside surface at high latitudes (as previously suggested by Sprague 1992 and Ip 1993).

Sprague, J. Geophys. Res., 97, 18257, 1992; Ip, Astrophys. J., 418, 451, 1993; Leblanc and Johnson, Icarus, In press 2003; Delcourt et al. Geophys. Let. Res., 29, 2002; Delcourt et al., Ann. Geophysicae, In press 2003.

The author(s) of this abstract have provided an email address for comments about the abstract: francois.leblanc@aerov.jussieu.fr

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Bulletin of the American Astronomical Society, 35 #4
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