Number of particles in the leading and trailing side of the horseshoe orbits during the outward migration and growth of Jupiter from 5 to 18 au. The blue line is the number of particles in the L₄ side of the horseshoe orbit (leading side) versus time and the green line is the number of particles in the L₅ side of the horseshoe orbit (trailing side) versus time. As expected, in the case of outward migration, particles spend more time in the trailing part of the orbit, because the path of the particles is wider on that side. Dashed lines indicate the time frame where Jupiter is growing and migrating.