Abstract: In this work we present several studies related to the modelling of solar variability and its possible physical causes. This is done in two parts: the rst one by approaching solar variability in the timescale of thousands of years and the second one using a timescale of decades or centuries.
In the first part we use a published reconstruction of the sunspot number for the last 11 millennia to build a variation profi le of solar luminosity over the last 7000 years.
Afterwards this curve is studied from a statistical point and some considerations regarding its reproducibility using a solar standard model are presented. In order to reproduce the observed variations in luminosity, the study hints that changes in the energy transport in the solar convection zone should occur. The second part is dedicated to the development of a simple model, derived from the mean fi eld dynamo theory, that can qualitatively explain the main features of the large scale magnetic fi eld responsible for the solar cycle. After presenting its main characteristics, the model is used to gain insight on the role of some physical mechanisms in the variability observed, as well as possible physical mechanisms behind solar grand minima episodes. With the help of the dynamical systems theory, the model is used to reconstruct the meridional circulation pro file for the last 250 years. Finally, we use a computational fl ux transport dynamo model to study the impact of the inferred meridional circulation profi le in the cycle's amplitude as well as to study the effect of stochastic fluctuations in a scenario where two "poloidal field regeneration" mechanisms (α effects) work in parallel to reproduce grand minima periods.
Keywords: solar activity, solar cycle, sunspots, solar dynamo, low order dynamo model, large scale magnetic fields evolutionv
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