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K. Ohtsuki (U. Colorado)
Collisions between particles play an essential role in dynamical evolution of planetary rings: they result in either rebound, accretion, or fragmentation of particles, and also cause angular momentum transport in rings. We obtained gravitational capture probability of colliding particles using three-body orbital integration, which takes into account velocity distribution and surface friction of particles. On the basis of our numerical results as well as N-body and statistical simulations, we will discuss accretional evolution of ring particles. On the other hand, oblique impacts between particles with rough surfaces lead to rotation. Observations of thermal emission from ring particles can provide information about their rotation states, and they would constrain particle properties and evolution. Recent works have shown that the mean angular momentum brought by a number of impacts of much smaller ring particles would lead small moonlets embedded in planetary rings to rotate slowly in the prograde direction. However, not only the mean values, but also dispersions in the rotation rates also need to be taken into account for rotation of ring particles. We will discuss rotation of ring particles and moonlets, on the basis of N-body simulation and three-body orbital integration.
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Bulletin of the American Astronomical Society, 36 #4
© 2004. The American Astronomical Soceity.