Evolution of the core rotation rate as a function of the stellar radius. All models have an initial mass of 1.2 M_⊙ and an initial velocity of 5 km s⁻¹ (P_ini = 12 days) and were computed with qcrMESA. Different values for the additional viscosity are used in each model, as indicated in the figure in units of cm² s⁻¹. The sharp drop in core rotation rate seen at R ∼ 150 R_⊙ occurs because of the helium flash. The data correspond to red giants and red clump stars from Mosser et al. (2012). Only stars (data) with an estimated mass lower than M ≲ 2 M_⊙ were included. Red clump stars are grouped at radii R ∼ 10 R_⊙ (crosses), and red giants in the hydrogen-shell burning phase are located above this, with a higher core rotation rate and lower radii (circles).