Axial viscous ∣Γ _ν , z∣ (blue) and electromagnetic torque ∣Γ _η , z∣ (orange) as a function of the Ekman number, Ek, applied on the mantle by core motions resulting from the m = 0 component of libration. Dimensionless values can be read from the left axis and dimensional values from the right axis. The lighter lines correspond to the case with no background stratification N(r) = 0 for 0.4 = r _ICB ≤ r ≤ r _CMB, and the darker lines correspond to the stratified case (Equation (20)) with N ₀ = 100, h = 0.1, r _C = 0.4, and r _ICB = 0.7. Extrapolation to the torques expected in Mercury’s core, represented by the filled circles, is performed along the dotted lines.