COLLISIONAL SIMULATIONS OF NEPTUNE RING ARCS

The currently accepted model for Neptune are confinement relies on the radial and azimuthal confining perturbations due to the nearby satell ite, Galatea. This model calls for are particle orbits exhibiting a ne gative eccentricity gradient and crossing at quadrature, a configurati on that paradoxically leads to collisions energetic enough to disrupt are confinement. We confirm with numerical collisional N-body simulati ons that the confinement mechanism relying on a 42:43 corotation-incli nation resonance and a 42:43 outer Lindblad resonance with Galatea is indeed capable of confining a large population of 10-m-size and bigger particles over short time scales. Moreover, we find that an 84:86 out er vertical resonance, also due to Galatea, falling within 20 m of the arcs' radial position, effectively reduces the collision frequency an d relative collisional velocities and consequently stabilizes the arcs over long time scales against the disruptive effects of collisions. ( C) 1997 Academic Press.