On the connection between solar surface magnetic flux and the total solar irradiance

Solar surface magnetic flux evolution plays a dominant role in the variability of total solar irradiance (TSI). Different proxies of magnetic activity have been introduced to correlate solar variability and TSI. We present the daily strong flux densities (SFDs) and weak flux densities (WFDs) defined with three magnetic thresholds calculated from the Solar Dynamic Observatory/Helioseismic Magnetic Imager. TSI measurements are from the radiometers of the Variability of Solar Irradiance and Gravity Oscillations experiment on the Solar and Heliosphere Observatory, and sunspot area (SSA) is from the National Oceanic and Atmospheric Administration. We characterize the influence of the magnetic flux density variation on the TSI using the Pearson, Spearman, and percentage bend correlations and wavelet analysis between the TSI and the flux density. The Pearson's correlation shows that the TSI is negatively and strongly correlated with SFD and moderately with SSA; Spearman and 20% bend correlation shows that the TSI is moderately correlated with SFD and weakly with SSA on solar maximum, but weakly correlated on solar minimum. However, the TSI is not correlated with WFD during solar maximum and minimum. The bootstrapping tests also confirm that the influence of SFD on TSI is more significant than that of SSA. Finally, a wavelet analysis supports the idea that the SFD and TSI have a causality linkage and that the SFD dominantly influences the TSI variability on the rotational timescale.