Dust Coagulation in the Vicinity of a Gap-Opening Jupiter-Mass Planet

TL;DR

This study investigates dust coagulation and compaction around a Jupiter-mass planet's gap using high-resolution MHD simulations combined with Monte Carlo modeling, revealing high porosity growth influenced by turbulence.

Contribution

It integrates MHD simulations with dust coagulation modeling to analyze dust growth and porosity in planet gap environments, a novel approach for this context.

Findings

Dust aggregates generally grow and compact, except in one specific case.

Final porosity ranges from 30% to 98%, depending on initial conditions.

Turbulent relative speeds drive the efficiency of dust compaction.

Abstract

We analyze the coagulation of dust in and around a gap opened by a Jupiter-mass planet. To this end, we carry out a high-resolution magnetohydrodynamic (MHD) simulation of the gap environment, which is turbulent due to the magnetorotational instability. From the MHD simulation, we obtain values of the gas velocities, densities and turbulent stresses a) close to the gap edge, b) in one of the two gas streams that accrete onto the planet, c) inside the low-density gap, and d) outside the gap. The MHD values are then supplied to a Monte Carlo dust coagulation algorithm, which models grain sticking and compaction. We consider two dust populations for each region: one whose initial size distribution is monodisperse, with monomer radius equal to 1 $\mu$m, and another one whose initial size distribution follows the Mathis-Rumpl-Nordsieck distribution for interstellar dust grains, with an initial range of monomer radii between 0.5 and 10 $\mu$m. Our Monte Carlo calculations show initial growth of dust aggregates followed by compaction in all cases but one, that of aggregates belonging to the initially monodisperse population subject to gas conditions outside the gap. In this latter case, the mass-weighted (MW) average porosity of the population reaches extremely high final values of 98\%. The final MW porosities in all other cases range between 30\% and 82\%. The efficiency of compaction is due to high turbulent relative speeds between dust particles. Future studies will need to explore the effect of different planet masses and electric charge on grains.