Project: PlanetsInBed - Embedded planets in wind-driven discs

Prace Call: 17th
ID: 2018184405, Leader: Colin McNally
Affiliation: Queen Mary University of London, UK
Research Field: Universe Sciences
Collaborators: Richard Nelson Queen Mary University of London UK , Oliver Gressel University of Copenhagen DK , Pablo Benitez-Llambay University of Copenhagen DK , Sijme-Jan Paardekooper Queen Mary University of London UK
Resource Awarded: 23.6 Mil. core hours on Joliot Curie - SKL

Abstract

Driven by the ever and rapidly increasing number of observed, and increasingly well-characterized, exoplanetary systems, understanding how planetary systems form is one of the most active areas in astrophysics. Crucial to this is understanding the protoplanetary disc from which these planets form, and how they interact with it. Forming planets in a disc nec-essarily drives gravitational interactions which cause the semimajor axis to evolve - a process known as migration. Both the formation process, composition, and final positions of planets can be affected by migration. Thus, understanding the mechanisms and dynamics of migra-tion torques is a longstanding central problem in planet formation theory. At the same time, protoplanetary discs have long posed significant theoretical challenges. Although significant accretion is observed onto central stars during the presumed planet-forming era, the mecha-nisms from which this material is driven through the disc have been problematic. The tradi-tional assumption of a weakly-specified turbulence giving rise to a turbulent viscosity and viscous accretion disc has been problematic, due to a lack of a sufficiently vigorous and ge-neric mechanism that can operate in these very low ionization discs. Studies of the magnetic configurations that arise in simulations including the non-ideal MHD effects which are the main stumbling block from viscous models has given rise to a viable alternative, a paradigm of nearly laminar wind-driven accretion discs. However, these discs, having very low turbulence and hence viscosity, give rise to qualitatively new types of migra-tion torques and behaviours. So far, our project team has studied a subset of these in two-dimensional simulations, but the most interesting case, in which a surface accretion flow driven at the top of the disc by the wind, cannot be reduced to a two-dimensional model. Having developed the necessary scientific background, codes, and setups, we will to attack this crucial three dimensional problem with PRACE Tier-0 resources.