Advection of Potential Temperature in the Atmosphere of Irradiated Exoplanets: A Robust Mechanism to Explain Radius Inflation

• Published in: The Astrophysical journal Vol. 841; no. 1; pp. 30 - 37
• Main Authors: Tremblin, P., Chabrier, G., Mayne, N. J., Amundsen, D. S., Baraffe, I., Debras, F., Drummond, B., Manners, J., Fromang, S.
• Format: Journal Article
• Language: English
• Published: Goddard Space Flight Center The American Astronomical Society 20-05-2017; American Astronomical Society; IOP Publishing
• Subjects: ADVECTION; ASTRONOMY; Astrophysics; ASTROPHYSICS, COSMOLOGY AND ASTRONOMY; Atmosphere; ATMOSPHERES; Atmospheric circulation; Atmospheric circulation models; atmospheric effects; Atmospheric heating; Atmospheric models; Atmospheric structure; COMPARATIVE EVALUATIONS; Conservation; COSMOLOGICAL INFLATION; Extrasolar planets; Gas giant planets; HEATING; IRRADIATION; JUPITER PLANET; LONGITUDINAL MOMENTUM; Lunar And Planetary Science And Exploration; methods: numerical; Oceans; planets and satellites: general; Potential temperature; Robustness; SATELLITES; STEADY-STATE CONDITIONS; Three dimensional models; THREE-DIMENSIONAL CALCULATIONS; Transit; Two dimensional models; TWO-DIMENSIONAL CALCULATIONS; Vertical advection; Tmospheric Effects; Methods: Numerical; Planets And Satellites: General
• ISSN: 0004-637X; 1538-4357
• DOI: 10.3847/1538-4357/aa6e57

The anomalously large radii of strongly irradiated exoplanets have remained a major puzzle in astronomy. Based on a two-dimensional steady-state atmospheric circulation model, the validity of which is assessed by comparison to three-dimensional calculations, we reveal a new mechanism, namely the advection of the potential temperature due to mass and longitudinal momentum conservation, a process occurring in the Earth's atmosphere or oceans. In the deep atmosphere, the vanishing heating flux forces the atmospheric structure to converge to a hotter adiabat than the one obtained with 1D calculations, implying a larger radius for the planet. Not only do the calculations reproduce the observed radius of HD 209458b, but also reproduce the observed correlation between radius inflation and irradiation for transiting planets. Vertical advection of potential temperature induced by non-uniform atmospheric heating thus provides a robust mechanism to explain the inflated radii of irradiated hot Jupiters.