Thermodynamics of Viscously Heated Circumplanetary Disks
Abstract
Circumplanetary disks (CPDs) play an important role in the formation of gas giants and their satellites, yet remain poorly understood owing to the lack of observables and comprehensive theoretical models. Incorporating α-viscosity, a free-fall prescription of mass infall and boundary layer accretion, we develop an axisymmetric viscous radiation hydrodynamic (RHD) model. We evolve this model for different physical parameters using the RHD code {\tt Guangqi}, which solves RHD equations under the flux-limited diffusion approximation. In eight out of nine simulations, we obtain quasi-steady-state solutions and verify self-consistent energy conversion and transport. Overall, disk thickness increases with accretion rate and decreases with planet mass, consistent with the expected trend in conventional α-disk models. On the other hand, we highlight that the boundary layer plays a significant role in setting angular momentum transport and thermodynamics of the inner CPD, yielding ``hot'' (sreal>11 kB mH−1) accreted gas, and potentially leading to dust sublimation. We identify a supersonic accretion flow, amounting to 2%--5% of the total accretion rate, located at high elevations above the CPDs with low angular momentum in our simulations. If the planet is massive (≳3 MJ), this low angular momentum flow impacting the planetary surface could generate observable Hα emission when the shock accretion rate is ≳5.5×10−8 MJ yr−1.
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BibTeX
@misc{chen2026thermodynamics,
title = {{Thermodynamics of Viscously Heated Circumplanetary Disks}},
author = {Zhuo Chen and Jing Yang and Xue-Ning Bai},
howpublished = {arXiv},
year = {2026},
month = oct,
doi = {10.48550/arxiv.2610.21284},
eprint = {2610.21284},
archivePrefix = {arXiv},
url = {https://arxiv.org/abs/2610.21284},
note = {CC BY 4.0},
}
RIS
TY - UNPB
TI - Thermodynamics of Viscously Heated Circumplanetary Disks
AU - Zhuo Chen
AU - Jing Yang
AU - Xue-Ning Bai
PY - 2026
DA - 2026/10/15
PB - arXiv
DO - 10.48550/arxiv.2610.21284
UR - https://arxiv.org/abs/2610.21284
AB - Circumplanetary disks (CPDs) play an important role in the formation of gas giants and their satellites, yet remain poorly understood owing to the lack of observables and comprehensive theoretical models. Incorporating α-viscosity, a free-fall prescription of mass infall and boundary layer accretion, we develop an axisymmetric viscous radiation hydrodynamic (RHD) model. We evolve this model for different physical parameters using the RHD code {\tt Guangqi}, which solves RHD equations under the flux-limited diffusion approximation. In eight out of nine simulations, we obtain quasi-steady-state solutions and verify self-consistent energy conversion and transport. Overall, disk thickness increases with accretion rate and decreases with planet mass, consistent with the expected trend in conventional α-disk models. On the other hand, we highlight that the boundary layer plays a significant role in setting angular momentum transport and thermodynamics of the inner CPD, yielding ``hot'' (s_real>11 k_B m_H^−1) accreted gas, and potentially leading to dust sublimation. We identify a supersonic accretion flow, amounting to 2%--5% of the total accretion rate, located at high elevations above the CPDs with low angular momentum in our simulations. If the planet is massive (≳3 M_J), this low angular momentum flow impacting the planetary surface could generate observable Hα emission when the shock accretion rate is ≳5.5×10^−8 M_J yr^−1.
ER -