Perturbed surface density of the MHD simulations. From left to right: increase in the strength of the magnetic field. In addition, for a given value of the magnetic field, we can also increase the Ambipolar coefficient value. For the lowest value of the magnetic field (left panel), we see the formation of a secondary ring at r = 2 au with our lower value of ambipolar diffusion (Λ_A = 10); thus, we do not run additional simulations in this case. In the case of β_m = 10⁵ (second panel and third panels) we observe a secondary ring for Λ_A = 10; however, the formation of a secondary well contrasted ring requires a higher ambipolar diffusion strength (Λ_A = 1, third panel). Finally, for β_m = 5 × 10³, there is no secondary ring formed for Λ_A = 10 (not shown) nor for Λ_A = 1 (fourth panel). We observe a poorly contrasted secondary ring for Λ_A = 0.1 (fifth panel). Finally, we observe a well contrasted secondary ring for Λ_A = 0.01 (right-most panel).