Evolution of the SEDs of nonthermal photons for the PWN. The model parameters are as follows: the pulsar and ejecta parameters are the same as those of the Crab nebula, except for the PWN age (the values are listed in Table 1), and the adopted parameters are α₁ = 1.5, α₂ = 2.5, E_b = 3.0 × 10⁵ MeV, η_B = 0.03, ϵ = 0.3, κ(t_ini) = 1.0 × 10²¹ cm² s⁻¹, and δ = 1/3. The solid lines represent the benchmark case. Left panel: dashed lines represent pure diffusion scenarios. Right panel: dashed lines represent pure advection scenarios.