Brightness variations of the Sun and Sun-like stars
Solar brightness varies on time scales from minutes to centuries and millennia, driven by the ever mutable granulation (convection) pattern on the solar surface and the perpetual evolution of the solar surface magnetic field. In parallel to solar studies, ground-based synoptic observations of Sun-like stars reveal analogous variations, although with a much wider variety of patterns. Furthermore, recent Kepler and Corot missions have provided light curves of Sun-like stars with unprecedented precision and thus opened a new era in study of stellar photometric variations.
The models developed by the MPS Sun-climate group have recently matured to reproduce solar brightness variations in great detail at all timescales that have until now been resolved or covered by observations. The magnetohydrodynamic simulations of stellar atmospheres which are being performed by the MPS Solar-MHD group as well as the new computationally efficient radiative transfer schemes which are being developed by the MPS Sun-climate group make it now possible to extend solar irradiance models to Sun-like stars.
A number of PhD projects are available, which can be more theory or data oriented, depending on the candidate profile. The projects are expected to answer the following questions:
- How do stellar photometric variabilities depend on the main stellar parameters (e.g. age, effective temperature, metallicity)?
- Why does decadal variability of solar brightness appear to be anomalously low in comparison with other stars with near-solar magnetic activity?
- How can one determine the basic properties of stellar magnetic cycles from stellar photometric records?
- What are the main criteria for distinguishing between photometric signatures of stellar variations and exoplanet transits?