Effect of the magnetic field parameters on the depolarisation profile of the cluster G039.85−39.98, with R₅₀₀ = 1.2 Mpc. The varied parameters are the central magnetic field strength B₀ in units of μG, the magnetic field power-law index n and the maximum correlation scale Λ_max in kpc. For all but one model, the maximum correlation scale was set to the maximum allowed by the image.