Drifts of pseudo-proper elements of orbits inside the J2:1 commensurability due to the diurnal Yarkovsky effect. The initial conditions are the same as those in Fig. 5 while the Yarkovsky effect is included in the force model (see the text for physical parameters related to the Yarkovsky effect). As in Fig. 5, the section Q₂ ≈ 0 (Q₂ ≈ π) in Eq. (23) is used to record the pseudo-proper elements of each orbit in frame a (frame b). The integration time is 2 Myr. The ν₅ resonance structures are taken from Fig. 4. The gray curves are the level curves of I₁ that the ν₅ libration approximately follows. Compared with Fig. 5, the pseudo-proper elements show obvious systematic drifts. The light yellow curves in frame a mark the pseudo-proper elements obtained using partial normal form H₂^* perturbed by ${{\overline{F}}_Y|}_J$, which agrees well with the reference results by the SWIFT package.