Magnetic field versus the age of a 0.9 M_⊙ star for three different initial rotation periods. At the base of the CZ (left panel), the magnetic field is estimated from the scaling laws listed in Table 1. At the top of the CZ (right panel), the same scaling laws are used to extrapolate a dipolar magnetic field near the surface (see Eq. (10)). The “stars” symbols () that represent mean dipolar magnetic fields at the surface of 0.9 M_⊙ stars are taken from See et al. (2017), and the age of the stars are from Ge et al. (2006), Janson et al. (2008), Line et al. (2015), and Folsom et al. (2016). Multiple observations of the dipolar magnetic field of a star are joined by a line.