Radio flux (Eq. (20)) as a function of stellar wind density and pressure for different efficiency factors. Colored solid and dashed lines represent fluxes for the open and closed MS models. Observational limits (Turner et al. 2021) are indicated by the gray shaded area. Horizontal gray lines display theoretical sensitivity limits of the LOFAR telescope. The real sensitivity for Stokes V signals obtained from Turner et al. (2019) is plotted as a yellow line. The vertical gray line marks the basic model (Table 1).