DPS 35th Meeting, 1-6 September 2003
Session 11. Planetary Rings I
Oral, Chairs: L. Spilker and C. B. Olkin, Wednesday, September 3, 2003, 1:30-3:00pm, DeAnza III

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[11.02] Influence of adhesion on collision dynamics: Applications to planetary rings near the Roche zone

N. Albers, F. Spahn (Inst. f. Physik, Universität Potsdam, Germany)

The collision dynamics of granular particles based on a viscoelastic contact model is extended to account for surface effects like adhesion and roughness. The normal and tangential restitution coefficients are calculated. In the pure viscoelastic case the restitution coefficient is a monotone decreasing function with increasing impact speed. Including adhesion, small impact velocities lead to a vanishing restitution. Thus, a sticking of particles occurs allowing for growth processes if no other forces, like tidal interactions, counteract.

Based on this dynamics it is possible to derive a mass and material dependent threshold velocity for the occurrence of aggregation. For particles in planetary rings, smaller than centimeters in size, adhesive attraction forces allow them to stick to larger particles or form larger aggregates. On the contrary, higher impact speeds are able to break these aggregates again.

In planetary rings near the Roche zone an interplay between aggregation and fragmentation may be the reason for a vivid size distribution dynamics on a relative short time scale. Such a combined dynamics of the velocity and size distribution may be of relevance for Saturn's F ring, which is just outside of Saturn's Roche zone. A coexistence of moonlets and ring particles might be the result of such formation and erosion processes.

This work is funded by the Studienstiftung des deutschen Volkes.

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