Parallel sessions

In the last two decades, realistic three-dimensional hydrodynamical simulations have become essential to understand modern observations of stars and their environment, ranging from Solar flares to spectral lines in cool stars, the imaging of circumstellar discs and transients resulting from stellar mergers. This session aims at discussing new results and current challenges related to 3D hydrodynamical simulations and sharing ideas between diverse research areas regarding their applications to observations, with a focus on the training of junior researchers. (i) Stellar astrophysics: The surface layers of cool stars, giants and white dwarfs are governed by convection, which requires an understanding of the complex interplay between compressible hydrodynamical flows, radiative cooling (RHD) and magnetic fields (MHD). Realistic numerical simulations of the atmospheres of convective stars are now within reach, but there is still extensive work needed to fully understand line formation, convective overshoot and interaction with pulsations. Hydrodynamical simulations of interiors stellar convection are also critical to understand stellar evolution, chemical mixing and nuclear burning rates. (ii) Exoplanet characterisation and atmospheres: Stellar atmospheric convection and magnetic activity can impact the interpretation of planet detections from radial velocities or transits, as well as the interpretation of exoplanet atmospheres observed via transmission and emission spectroscopy. In addition, hydrodynamics models of planet atmospheres can inform on global heat transport and circulation, chemistry, and infrared spectra. (iii) Solar physics: The generation of magnetic fields by a large-scale dynamo is linked to the significant activity of the Sun, including the emergence and disappearance of active regions, as well as flare events and mass ejections. High resolution spatial and time cadence MHD simulations are essential to understand the physical processes underlying the highly dynamical plasma and magnetic field evolution through the atmosphere, chromosphere and corona. (iv) Circumstellar disks: Hydrodynamical simulations are key to understand circumstellar discs ranging from protoplanetary discs to those that form from disrupted rocky planetesimals around old white dwarfs. Important questions including dust growth and fragmentation in self-gravitating discs, and the modelling of gap and ring features that are common in planet-forming discs. (v) Transients: With the discovery of the first gravitational wave events, there has been renewed interest in hydrodynamical simulations of stellar mergers including compact neutron stars and white dwarfs. Furthermore, 3D hydro simulations of core-collapse and type Ia supernovae have matured significantly in recent years, helping to understand a vast range of transients and their underlying stellar populations.