DPS 2001 meeting, November 2001
Session 32. Rings II
Oral, Chair: H. Throop, Thursday, November 29, 2001, 2:40-3:30pm, Regency GH

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[32.04] Reconstructing Saturn's OH Cloud

S. Jurac, J. D. Richardson (M.I.T.), R. E. Johnson (University of Virginia), M. A. McGrath (Space Telescope Science Institute), V. M. Vasyliunas (Max Planck Institut for Aeronomie), A. Eviatar (Tel Aviv University)

The source of water-like neutral molecules in Saturn's magnetosphere has been a topic of considerable interest since the HST discovery of a dense OH torus. Measured OH densities were more than an order of magnitude larger than predicted and thus raised the question of what mechanism was responsible for generating neutrals and plasma in that region. It was suggested that the neutrals could be produced by sputtering or micrometeorite erosion of rings and satellites, or by hyper-velocity collisions of small E-ring grains with larger objects.

Here we extend our Monte-Carlo model, which follows the orbital dynamics and chemistry of neutral species, to account for collisions between plasma ions and neutrals. It is shown that the collisional energy transfer introduces a significant spread of the OH cloud from the source region. Consequently, the total H2O source rate, which is a free parameter in our model, must be significantly larger than previous estimates in order to reproduce HST measurements. Our model shows that the source region is narrowly constrained to the Enceladus/E-ring region, which is the dominant supplier of neutrals in Saturn's inner magnetosphere. This work is supported by NASA Planetary Atmospheres Grant.

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