@InProceedings{Vieira:2018:EsSoLu,
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
24",
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 = "29 mar. 2024"
}