Effect of different viscosity parameters on the location and evolution of pressure bumps. Panels (a) and (b): Comparison between the models alDZ4 and MREF^* (separated by the dotted grey line) in terms of the evolution of the surface density and κ²/Ω² for a density bump placed by the respective outburst cycles. The depicted time frame is the same for both models and begins at a time t₀ at which both models have roughly the same minimum value of κ²/Ω². The time t₁ = t₀ + ∆t has been chosen arbitrarily. Panels (c) and (d): Surface density and the radial gradient of the vortensity for four different models in the radial range of the DZIE. The vertical dashed lines in panel (c) mark the positions of the inner pressure bumps in the respective models of the same colour. The inset panel (d₁ ) presents κ²/Ω² for the model alDZ4 around the position of the vortensity minimum. The dashed green lines in panels (b) and (d₁) indicate the upper limit for the halfway-to-Rayleigh criterion.