The aim of the proposed multi-disciplinary team is to bring together experts in solar variability, stellar physics, and data analysis to achieve two fundamental goals:

–  G1. Apply our knowledge of the Sun to understand stellar brightness variations and thus improve the techniques for detection and characterisation of exoplanets.

–  G2. Analyse newly-available stellar photometric data to assess the full possible range of solar variability.

These goals have been prompted by the recent progress in modelling of solar/stellar atmospheres and new state-of-the-art stellar photometric data. In particular:

  • Our understanding of solar brightness variations has dramatically improved over the last few years due to extended measurements having improved precision and stability;
  • New 3D magneto-hydrodynamic (MHD) simulations of flows and magnetic fields in the near- surface layers of the Sun and stars as well as time-efficient radiative transfer codes now make it possible to extend very successful models of solar brightness variations to other stars;
  • An unprecedented level of photometric precision of broadband stellar photometry has been achieved by the CoRoT and Kepler space-based missions and is anticipated with the launch of the TESS, CHEOPS, and PLATO missions, while automated ground-based telescopes have dramatically increased the number of stars observed over their activity cycles.

Intrinsic stellar brightness variation is a limiting factor for exoplanet characterisation via transit photometry. Similarly, solar brightness variability is one of the main natural forcings of Earth’s climate system. Consequently, our stated goals G1 and G2 have far-reaching implications that go well beyond solar and stellar physics. Furthermore, by helping experts in stellar and solar brightness variations work together we aim to bring closure to the long-time question of whether solar variability is typical or anomalous with respect to stars with near-solar age. One of the outcomes of the team will be a thorough comparative review of solar and stellar activity, which will be the first of its kind.

The unique, highly multi-disciplinary composition of the team consisting of world-leading experts in the fields of solar irradiance, stellar variability, and data analysis will put it in the pole position for raising our understanding of solar-stellar connections to a new level. The format of the ISSI meetings is ideally suited to support extended collaborations between complementary groups such as those of our proposed team.