Combined effects of disc winds and turbulence-driven accretion on planet populations

Abstract

ABSTRACT Recent surveys show that protoplanetary discs have lower levels of turbulence than expected based on their observed accretion rates. A viable solution to this is that magnetized disc winds dominate angular momentum transport. This has several important implications for planet formation processes. We compute the physical and chemical evolution of discs and the formation and migration of planets under the combined effects of angular momentum transport by turbulent viscosity and disc winds. We take into account the critical role of planet traps to limit Type I migration in all of these models and compute thousands of planet evolution tracks for single planets drawn from a distribution of initial disc properties and turbulence strengths. We do not consider multiplanet models nor include N-body planet–planet interactions. Within this physical framework we find that populations with a constant value disc turbulence and winds strength produce mass–semimajor axis distributions in the M–a diagram with insufficient scatter to compare reasonably with observations. However, populations produced as a consequence of sampling discs with a distribution of the relative strengths of disc turbulence and winds fit much better. Such models give rise to a substantial super Earth population at orbital radii 0.03–2 au, as well as a clear separation between the produced hot Jupiter and warm Jupiter populations. Additionally, this model results in a good comparison with the exoplanetary mass–radius distribution in the M–R diagram after post-disc atmospheric photoevaporation is accounted for.