Negative diffusion in planetary rings with a nearby moon

► We simulate the evolution of narrow planetary rings perturbed by a nearby moon. ► A forced eccentricity greater than 3 × 10−5 can cause rings to decrease their width by 90%. ► Ring particle collisions in the peaks of the satellite wake cause the decrease in width. ► The unperturbed ring optical depth must be greater than 0.03. ► The process is not very sensitive to particle size distribution or particle self-gravity.