Evolution of test particle orbits, taken from the benchmark model simulation, in ω−a plane. The strength of EFE was assumed to be Q₂ = 1. Only particles surviving at least 3 Gyr are taken into account. The evolutionary tracks of the particles are shown in the last Gyr of the simulation every time their orbits met the criteria, i.e. i< 50 deg, q< 80 au. The tracks below a = 500 au are not shown as these are just full-width horizontal lines.