Solar variability: the connection between solar surface magnetic flux and TSI

                  Abstract

Solar surface magnetic field evolution plays a dominant role in the variability of Total Solar Irradiance (TSI) modulating the appearance of various features (e.g., sunspots, faculae, network, etc.) on the solar surface. Different proxies of magnetic activity have been introduced to study or correlate solar variability and TSI. In this work, we present a couple of solar surface magnetic flux indices: the daily strong field density (SFD) and weak field density (WFD), which
are calculated from SDO/HMI. These are defined on the basis of a suitable magnetic threshold and can be associated with solar active regions that we assume to be related to short (daily) and long (solar rotation) time scales. In the analysis, we used TSI data from the radiometers of the VIRGO of the SOHO Mission. More in detail, we present the characterization of the influence of the magnetic field flux variation, described by SFD and WFD proxies, on the TSI using the Pearson correlation and wavelet analysis. The Pearson correlation shows that SFD is negatively correlated with TSI, with a strong correlation coefficient of -0.85, while WFD is not correlated. The bootstrapping tests also confirm
that the influence of SFD on TSI is more significant than that of WFD. Finally, the wavelet analysis between SFD and TSI supports the idea that the SFD and TSI have a causality linkage at the solar rotational time scale, while the same analysis indicates that the SFD dominantly influences the TSI variability in the rotational time
scale.