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[21.04] Escape of Nitrogen from Titan's atmosphere driven by magnetospheric and pick-up ions

M. Michael (Materials Science and Astronomy, U. Virginia), M. Liu, R. E. Johnson (Materials Science and Engineering, U. Virginia), J. G. Luhmann (Space Sciences Lab., UC, Berkeley), V. I. Shematovich (Institute of Astronomy, RAS, Russia)

The nitrogen rich atmosphere of Titan is a significant source of the neutrals in Saturn's magnetosphere. As Titan does not posses an intrinsic magnetic field, energetic Kronian magnetospheric ions penetrate Titan's atmospheric exobase as can local pick-up ions (e.g. Shematovich et al. 2003). Penetration by energetic ions is described here using a 3-D Monte Carlo model. The incident ions can lead directly or indirectly to the production of fast neutrals that collide with other atmospheric neutrals. This leads to dissociation and the ejection of both atomic and molecular nitrogen. The recently calculated dissociation cross sections of N₂ are used in the present model (Tully and Johnson 2002). The incident flux of slowed magentospheric N⁺ ions and pick-up C₂H₅⁺ ions is estimated from the work of Brecht et al. (2000). These ions of energy less than 1.2 keV are shown to be more efficient in ejecting material from Titan's atmosphere than the higher energy corotating ions described in early estimates (Lammer et al. 1998). This incident flux of ions are used in the model and the results are used as a source of nitrogen for the Saturnian plasma torus.

Acknowledgment: This work is supported by NASA’s Planetary Atmospheres Program.

References

Brecht, S.H., J.G. Luhmann, and D.J. Larson, J. Geophys. Res., 105, 13119, 2000.

Lammer, H. W. Stumptner, and S.J. Bauer, Planet. Space Sci., 46, 1207, 1998.

Shematovich, V.I., R.E. Johnson, M. Michael and J.G. Luhmann, J. Geophys. Res., in press, 2003.

Tully, C., R.E. Johnson, J. Chem. Phys. 117, 6556-6561, 2002.

The author(s) of this abstract have provided an email address for comments about the abstract: mm2eq@virginia.edu

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Bulletin of the American Astronomical Society, 35 #4
© 2003. The American Astronomical Soceity.