Logarithms of the spin parameter (ν) and stabilityratio as functions of the forcing period (days) in logarithmic scale. The blue dashed line designates the transition between the inertial and sub-inertial regimes (see Fig. 4), which occurs for τ_tide = τ_orb, the parameter τ_orb = 2π∕n_orb being the orbital period. The red dashed line corresponds to the Ω = 0 case. “Rotation (−)” and “Rotation (+)” stand for retrograde and prograde rotation, respectively. The green dashed line delimits the boundary of the asymtotic domain where the stable stratification dominates rotation in the radiative zone (), which is the condition of applicability of the traditional approximation in the sub-inertial regime.