DPS 35th Meeting, 1-6 September 2003
Session 20. Planetary Rings II
Poster, Highlighted on, Wednesday, September 3, 2003, 3:00-5:30pm, Sierra Ballroom I-II

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[20.06] Thermal radiation from Saturnís rings: new results on the spin of particles

C. Leyrat, C. Ferrari (Equipe GammaG, University Paris 7 and SAp/DAPNIA/DSM/CEA Saclay), L. Spilker (JPL/Caltech), S. Charnoz (Equipe GammaG, University Paris 7 and SAp/DAPNIA/DSM/CEA Saclay)

The dynamical evolution of dense ring systems is strongly dependent on inter-particle collisions and their mutual gravitational interactions. The ring local thickness and the energy stored in particles spins during collisions are revealing the microphysics of rings. However, the distribution of particles spins in Saturn's rings is yet unknown and the vertical structure is still under debate. Observations of ring temperatures at infrared wavelengths provide unique constraints on particles properties like their thermal inertia or their spin. Mid-infrared CAMIRAS/CFHT images, have shown that particles in Saturnís rings are most probably slow rotators with a very small thermal inertia, about 3 and 6 J.m≤.K-1.s-1/2 for B and C rings respectively (Ferrari et al. 2003). In order to more accurately constrain the spin of particles, we have developed a new model for the thermal radiation of a ring, which takes into account particles spins and assumes a monolayer vertical structure for now. We will show how spin norm and direction induce azimuthal variations in ring temperature and how these are affected by the position of the observer. Spin distributions derived from local numerical simulations (see Charnoz et al. this issue) are also included and tested against observations. This model is compared to currently available infrared data sets (CAMIRAS/CFHT, IRIS/VOYAGER, Ö). But the CIRS instrument on board the CASSINI spacecraft will soon allow us to closely constrain this spin distribution for all the Saturn's main rings thanks to the wide variety of observation geometries provided by the designed Tour and a wide coverage in ring azimuth.

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