Variation of I₂ (blue) and I₃ (red) for three orbits. Over the short time-length of the order of an average rotation period (Δt  =  3), the variations of the quasi-integrals are significantly smaller compared to the variations over long periods. The largest variations of the quasi-integrals are observed for I₃(∼ − 0.2) (bottom curve) of the box orbit (I₂ ∼ 0). The sharp variations of I₃ are related to the passage at the pericentre. The short-axis tube (I₂  ∼  I₃  ∼  0.1) and the long-axis tube (I₂ ∼ −0.1 and I₃  ∼  0.5) orbits have smoother variations of the quasi-integrals.