Calcium plage intensity and solar irradiance variations

We have established a statistical relation between the facular contribution to the solar irradiance and the intensity of the associated calcium plage. For the solar irradiance data the ACRIM measurements were used. The quiet-Sun level of the irradiance was determined as a function of the time for the period studied. A sample of plages in the period of the solar activity minimum was selected, during the periods when no spots were present on the solar disc. We have expressed the dependence studied through the parameter C sub(p) in the `proxy' PFI concept. The parameter C sub(p) could be related to the plage intensity (I) as C sub(p) =0.006I+0.003. The mean value of the parameter C sub(p) ranged between 0.015 and 0.017 depending on the choice of samples.