  Voyager 2 images confirmed the presence of ring arcs around Neptune. These
structures need a confinement mechanism to constrain their spreading due to
collisions, dissipative forces, and differential keplerian motion. Here we
report the results of a set of numerical simulations of the system formed by
Neptune, the satellite Galatea, dust ring particles, and hypothetical
co-orbital satellites. This dynamical system depicts a recent confinement
mechanism formed by four co-orbital satellites being responsible for the
azimuthal confinement of the arcs, while Galatea responds for their radial
confinement. After the numerical simulations, the particles were divided into
four groups: particles that stay in the arcs, transient particles, particles
that leave the arcs to the Adams ring, and particles that collide with the
co-orbital satellites. Our results showed that in all arcs the lifetime of the
smaller particles is at most 50 years. After 100 years about 20% of the total
amount of larger particles is still present in the arcs. From our numerical
simulations, the particles should be present in all arcs after 30 years, the
period between the discovery of the arcs up to now. Our results can not explain
the disappearance of the leading arcs, Liberte and Courage unless the arcs are
formed by different particle sizes. Analysis of the dust production, due to
collisions between interplanetary debris onto the surface of the co-orbital
satellites, ruled out the hypothesis that small satellites close to or in the
arc the structure could be its source.
