Dynamically Coupled Three-dimensional Cloud-Chemistry in Rapidly Rotating Irradiated Atmospheres: an Application to the Compact White Dwarf-Brown Dwarf system ZTFJ0038+2030
Abstract
Clouds and disequilibrium chemistry shape the observable properties of substellar and planetary atmospheres, and JWST time-resolved spectroscopy now enables direct tests of their three-dimensional structures. We present an update to the 3D atmospheric framework ADAM, coupling the dynamical core to a miniature kinetic chemistry scheme (mini-chem) and a saturation-relaxation tracer cloud module. Using this framework, we investigate the atmosphere of the brown dwarf orbiting the white dwarf ZTFJ0038+2030 in a 10-hour orbit. The brown dwarf receives stellar irradiation comparable to its internal heat flux, placing the atmosphere in a regime where the circulation is characterized by a standing Matsuno--Gill wave response and equatorial superrotation. Rapid rotation confines these structures closer to the equator, producing more symmetric broadband light curves with smaller hotspot offsets than canonical hot Jupiters, in agreement with recent JWST observations of this system. Although most species are globally homogenized, rapid rotation limits global-scale horizontal mixing and allows circulation-driven vertical transport to maintain strong CO and CO2 inhomogeneities in the photosphere. These chemical inhomogeneities produce asymmetric phase curves in the CO and CO2 absorption bands, which could qualitatively explain the observed CO2 light-curve asymmetry. When clouds are included, Na2S clouds dominate the photosphere and weaken the large-scale circulation, lowering photospheric CO and CO2 abundances, while MgSiO3 and Fe clouds rain out at deeper levels. Because the dominant Na2S clouds reside mostly above the quench region, cloud-driven convection has limited impact on the quenched abundances, which are instead regulated mainly by large-scale circulation.
Related
- Irradiated Atmospheres VII. Effect of Mixing Energy Flux on Atmosphere-Interior Coupling
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- Plasma chemistry and electron-moderated pathways in substellar atmospheres: a new perspective on the L/T transition
BibTeX
@misc{lai2026dynamically,
title = {{Dynamically Coupled Three-dimensional Cloud-Chemistry in Rapidly Rotating Irradiated Atmospheres: an Application to the Compact White Dwarf-Brown Dwarf system ZTFJ0038+2030}},
author = {Yanhong Lai and Xianyu Tan and Daphne Broski-Laing and Yifan Zhou and Sarah L. Casewell and Jenni R. French and Elspeth K. H. Lee and Joshua D. Lothringer and Vivien Parmentier and Shang-Min Tsai},
howpublished = {arXiv},
year = {2026},
month = oct,
doi = {10.48550/arxiv.2610.17714},
eprint = {2610.17714},
archivePrefix = {arXiv},
url = {https://arxiv.org/abs/2610.17714},
note = {CC0},
}
RIS
TY - UNPB
TI - Dynamically Coupled Three-dimensional Cloud-Chemistry in Rapidly Rotating Irradiated Atmospheres: an Application to the Compact White Dwarf-Brown Dwarf system ZTFJ0038+2030
AU - Yanhong Lai
AU - Xianyu Tan
AU - Daphne Broski-Laing
AU - Yifan Zhou
AU - Sarah L. Casewell
AU - Jenni R. French
AU - Elspeth K. H. Lee
AU - Joshua D. Lothringer
AU - Vivien Parmentier
AU - Shang-Min Tsai
PY - 2026
DA - 2026/10/13
PB - arXiv
DO - 10.48550/arxiv.2610.17714
UR - https://arxiv.org/abs/2610.17714
AB - Clouds and disequilibrium chemistry shape the observable properties of substellar and planetary atmospheres, and JWST time-resolved spectroscopy now enables direct tests of their three-dimensional structures. We present an update to the 3D atmospheric framework ADAM, coupling the dynamical core to a miniature kinetic chemistry scheme (mini-chem) and a saturation-relaxation tracer cloud module. Using this framework, we investigate the atmosphere of the brown dwarf orbiting the white dwarf ZTFJ0038+2030 in a 10-hour orbit. The brown dwarf receives stellar irradiation comparable to its internal heat flux, placing the atmosphere in a regime where the circulation is characterized by a standing Matsuno--Gill wave response and equatorial superrotation. Rapid rotation confines these structures closer to the equator, producing more symmetric broadband light curves with smaller hotspot offsets than canonical hot Jupiters, in agreement with recent JWST observations of this system. Although most species are globally homogenized, rapid rotation limits global-scale horizontal mixing and allows circulation-driven vertical transport to maintain strong CO and CO_2 inhomogeneities in the photosphere. These chemical inhomogeneities produce asymmetric phase curves in the CO and CO_2 absorption bands, which could qualitatively explain the observed CO_2 light-curve asymmetry. When clouds are included, Na_2S clouds dominate the photosphere and weaken the large-scale circulation, lowering photospheric CO and CO_2 abundances, while MgSiO_3 and Fe clouds rain out at deeper levels. Because the dominant Na_2S clouds reside mostly above the quench region, cloud-driven convection has limited impact on the quenched abundances, which are instead regulated mainly by large-scale circulation.
ER -