Libration amplitude of resonant angle ϕ for initial eccentricity e = 0.2 on (a, ω) plane (left), and (a, i) plane (right). The left panel is for coplanar configuration (i = i₈, Ω = Ω₈) and the initial mean anomaly is fixed as M = M₈. The right panel is for the inclined orbits with fixed initial argument of pericenter ω = −3° (see text). The libration amplitude is indicated by colour. Because the horseshoe resonance configuration encompasses both asymmetric islands, an abrupt change in libration amplitude can be seen at the separatrix.