Evolution of , evaluated in the middle of the convective envelope (at r = ΔR_CZ/ 2), as a function of stellar age (in logarithm scales) computed using the grid of rotating stellar models for 0.6 M_⊙ (dashed brown line), 0.7 M_⊙ (dashed red line), 0.8 M_⊙ (dashed orange line), 0.9 M_⊙ (dashed green line), 1 M_⊙ (dashed blue line), 1.1 M_⊙ (dashed purple line) and 1.2 M_⊙ (solid black line) stars. The critical convective Rossby number giving the transition between the rapidly and the slowly rotating regimes is represented by the solid thick grey line.