Time‐frequency analysis of total solar irradiance variations

Continuous wavelet analysis of the Total Solar Irradiance (TSI) time series accurately describes its non‐stationary, multi‐scale variations over a wide time‐scale domain. The analysis was also applied to Photometric Sunspot Index (PSI) and full‐disk Calcium II K‐line Photometric Facular Index (PFI) time series to identify the contributions of sunspots and faculae/magnetic‐network to the time‐frequency behavior of TSI. Significant spectral power is found near 27‐days in the time series spectra of TSI, PSI and PFI, confirming sunspot and facular phenomena as the primary causes of TSI variability near the average solar rotation rate for active regions. The spectra of both PFI and TSI exhibit correlative trends to longer periodicities during solar cycles 21 and 22, demonstrating the dominant influence of faculae and magnetic network on TSI during the declining phase of these solar cycles.