author = "Vieira, Lu{\'{\i}}s Eduardo Antunes",
          affiliation = "{Instituto Nacional de Pesquisas Espaciais (INPE)}",
                title = "Estimate of the solar luminosity variability for cycles 23 and 
                 year = "2018",
         organization = "Cospar Scientific Assembly, 42.",
             abstract = "The effect of the solar activity on the solar luminosity, which is 
                         the total electromagnetic solar output, is one of the fundamental 
                         questions in solar physics. Changes of the solar luminosity can 
                         arise from changes of the energy flux in the convection zone that 
                         can also affects other solar parameters such as the surface 
                         temperature, the apparent radius and shape, and the symmetry of 
                         the radiative field itself. Additionally, understanding the 
                         latitudinal distribution of the flux density is needed to compare 
                         the solar variability and its stellar analogues. Nevertheless, our 
                         observations of the solar flux density are limited to a region 
                         near the ecliptic plane, which have provided just a raw estimate 
                         of the variability of the solar luminosity. Here we present a 
                         reconstruction of the solar flux density and solar luminosity for 
                         the solar cycle 23 and ascending phase of cycle 24. The 
                         reconstruction is based on a combination of a state-of-art solar 
                         surface magnetic flux transport model and a semi-empirical total 
                         and spectral irradiance model. The flux transport model is based 
                         on assimilation of MDI/ SOHO and HMI/SDO magnetograms. The 
                         irradiance models free parameters are estimated by minimizing the 
                         difference between the models output and the PMOD Composite of TSI 
                         measurements. We have obtained a good agreement between the models 
                         output and the measurements. The distribution of active regions 
                         leads to a clear low latitude brightening during the solar 
                         maximum. This brightening results from the balance of the 
                         contributions from bright (faculae and network) and dark features 
                         (sunspots) located in the solar surface, which peaks near the 
                         solar equator. As the effects of dark features are limited to a 
                         narrower region, the variability of the flux density at the poles 
                         is dominated by the evolution of faculae and network. The 
                         preliminary results indicate that the heat flux blocked by 
                         sunspots is lower than the flux leaked by bright features. 
                         Consequently, an increase of the luminosity through the cycle is 
                         observed as previously estimated based on near ecliptic 
                         measurements. This work also enables an assessment of the 
                         properties of solar variability when viewed from out of the 
                         ecliptic, i.e., such as we might be viewing other stars of solar 
                         activity level. Finally, the limitations of the model and future 
                         strategies to extend the reconstruction of the flux density and 
                         solar luminosity will be presented.",
  conference-location = "Pasadena, California",
      conference-year = "14-22 July",
             language = "en",
           targetfile = "vieira_estimate.pdf",
        urlaccessdate = "25 jan. 2021"