Formation of narrow ringlets in Saturn's rings

The interaction between satellites and planetary rings takes mainly place in resonance locations, where the ratio of angular velocity of the ring particles and the satellite can be described with small integer numbers (e.g. 2:1, 4:3). In these locations the collisionally induced outward flow of the angular momentum is perturbed by the satellite. In some cases the perturbations may be strong enough to change the direction of the angular momentum flow. As a result the interparticle collisions will tend to increase density gradient, leading to formation of gaps, sharp edges, or narrow ringlets. Numerical 3-dimensional collisional simulations including satellite perturbations can capture the essence of this process.