Global 3D Radiation-Hydrodynamics Calculations of the Envelopes of Forming Planets Interacting with a Protoplanetary Disk

English Abstract:

We present 3D radiation-hydrodynamics calculations of envelopes of forming planets, during the phase of sustained solids' accretion. The planets reside in a protoplanetary disk at orbital radii a_p=5 and 10 AU from a sun-like star, and are assumed to have formed according to the Core Nucleated Accretion scenario. The planets have cores ranging from 5 to 15 Earth masses. The protoplanetary disk extends radially from a_p/2 to 2a_p. The planets' envelopes are resolved at the core-radius length scale by using a system of nested grids. The gas is assumed to be a solar mixture of H2, H, He, and their ions. The equation of state includes contributions from non-translational states of H2 and from ionization of atomic species, as well as from radiation energy. The dust opacity assumes a distribution of grains ranging from 5e-6 to 1 mm and multiple grain species. The opacity calculation applies the Mie theory for non-porous particles. We use 1D calculations of planet formation to supply the 3D calculations with solids accretion rates. Results show that temperatures, masses, and gas accretion rates of 1D and 3D envelopes agree within factors of 2. Passive tracers are employed to study the circulation of the gas flow around the cores and identify the spherical region of bound gas, which formally defines the envelope of the planet. We find envelope radii comparable to or smaller than the Bondi radius, and significantly smaller than the Hill radius. We find differential (i.e., depth-dependent) rotation at the envelope equators, and an overall slow bulk rotation of the envelopes compared to that of the solar system outer planets. Yet, specific angular momenta of the planets are comparable to those of the solar system giant planets. The polar flattening is estimated at values <~0.05. We also use passive tracers to study the dynamics of the accretion flow. We find that this flow is not isotropic around the planet and characterize its angular dependence. We find that it preferentially impacts the envelope surface at mid to high latitudes. Support from NASA Outer Planets Research and Origins of Solar Systems Programs is gratefully acknowledged. Computing resources were provided by the NASA High-End Computing Program through the NASA Advanced Supercomputing Division at Ames Research Center.