Power spectra of brightness variations of star rotating with a 30-day period plotted on logarithmic (upper panels) and linear (middle panels) scales. Also plotted are the gradients of the power spectra (lower panels). The calculations presented in left and right hand panels have been performed with the same set of model parameters (see text for details) but are associated with two different realizations of active regions emergences. Black, red, and blue curves correspond to total brightness variations (calculated with S_fac ∕S_spot = 5.5), as well as their facular and spot components, respectively. Numbers in the middle panels indicate peaks in the power spectra, while numbers in the lower panels point to positions of the inflection points.