Protoplanets in radiative disks and their circumplanetary environments

Advisor: Ondřej Chrenko (AI FMP CUNI)

Funding: Fully funded

Website: https://sirrah.troja.mff.cuni.cz/~chrenko/

Understanding planet-disk interactions and circumplanetary disk physics is at the forefront of numerical modeling in planet formation and plays a pivotal role in interpreting ALMA, JWST, and future ELT observations.

The goal of this project is to perform global simulations of a protoplanetary disk with an embedded planet while resolving the circumplanetary environment in detail. The simulations will include radiation transfer in the flux-limited diffusion approximation, as well as direct tracking of dust grains using a multi-fluid approach. We will extend the existing radiative model of the advisor (e.g., Chrenko & Lambrechts 2019, Chrenko et al. 2025) based on Fargo3D (Benítez-Llambay & Masset 2016), incorporating non-uniform grid spacing (Benítez-Llambay et al. 2023) to achieve high circumplanetary resolution. Alternatively, the applicant is welcome to adapt a different hydrodynamic code suitable for the task.

Possible applications and open scientific questions to choose from include:

Dust in circumplanetary disks and envelopes. It is not yet fully understood under which conditions planets form a circumplanetary disk (CPD) or an envelope. CPD formation appears to require the planet mass to be super-thermal (Sagynbaeva et al. 2025) and the local cooling time to be short (Krapp et al. 2024). The goal here will be to analyze the ability of the circumplanetary environment to retain dust grains of various sizes (to constrain the circumplanetary dust-to-gas ratio under different conditions). A range of planet masses and orbital distances will be considered.
Thermal processing and volatile sublimation. The local heating within the circumplanetary region can sublimate certain ices (such as CH4 as in Jiang et al. 2023, or CO as in Chrenko et al. 2025), enhancing local gas-phase abundances and facilitating rich chemistry. The aim will be to identify such processes in models with resolved CPDs and assess their potential observational signatures.
Migration of sub-Neptunes. Several studies suggest that close-in sub-Neptunes orbiting within the disk’s dead zone actually exceed the thermal mass criterion and open moderately deep gaps (Chrenko et al. 2022, Ziampras et al. 2025). To correctly understand the transition from Type I to Type II migration, it is vital to resolve the circumplanetary flow and assess the gravitational influence of the gas in the immediate vicinity of the planets.

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