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This paper contributes to the field of modeling and hindcasting of the totalsolar irradiance (TSI) based on different proxy data that extend further backin time than the TSI that is measured from satellites.  We introduce a simple method to analyze persistent frequency-dependentcorrelations (FDCs) between the time series and use these correlations tohindcast missing historical TSI values. We try to avoid arbitrary choices ofthe free parameters of the model by computing them using an optimizationprocedure. The method can be regarded as a general tool for pairs of data sets,where correlating and anticorrelating components can be separated intonon-overlapping regions in frequency domain.  Our method is based on low-pass and band-pass filtering with a Gaussiantransfer function combined with de-trending and computation of envelope curves.  We find a major controversy between the historical proxies andsatellite-measured targets: a large variance is detected between thelow-frequency parts of targets, while the low-frequency proxy behavior ofdifferent measurement series is consistent with high precision. We also showthat even though the rotational signal is not strongly manifested in thetargets and proxies, it becomes clearly visible in FDC spectrum.  The application of the new method to solar data allows us to obtain importantinsights into the different TSI modeling procedures and their capabilities forhindcasting based on the directly observed time intervals.

Method of frequency dependent correlations: investigating the variability of total solar irradiance