Maximum contrast of differential rotation inside the DZ as a function of P_r(N₀/Ω₀)²Re_c. The different symbols circle, square, hexagon and triangle respectively correspond to the simulations performed at Re_c = 10⁻¹, 5 × 10⁻¹, 1, and 2. Runs carried out at L_u = 5 × 10⁴ are presented in light blue, and those at L_u = 10⁵, in blue. The other parameters are P_r(N₀/Ω₀)² = 10⁻¹, E = 10⁻⁵, P_m = 10², and ρ_i/ρ₀ = 20.85 (runs D21–D24 and D27–D30 of Table 1).