Variation of solar irradiance and mode frequencies during Maunder   minimum
  Using the sunspot numbers reported during the Maunder minimum and the empirical relations between the mode frequencies and solar activity indices, the variations in the total solar irradiance and 10.7 cm radio flux for the period 1645 to 1715 is estimated. We find that the total solar irradiance and radio flux during the Maunder minimum decreased by 0.19% and 52% respectively, as compared to the values for solar cycle 22. 
A. Bhatnagar, Kiran Jain, S.C. Tripathy (Udaipur Solar Observatory,   PRL)