Title: Advection of potential temperature in the atmosphere of irradiated exoplanets: a robust mechanism to explain radius inflation,
Abstract: The anomalously large radii of strongly irradiated exoplanets have remained a
major puzzle in astronomy. Based on a 2D steady state atmospheric circulation
model, the validity of which is assessed by comparison to 3D calculations, we
reveal a new mechanism, namely the advection of the potential temperature due
to mass and longitudinal momentum conservation, a process occuring in the
Earth's atmosphere or oceans. At depth, 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 HD209458b, but also 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 explaining the inflated radii of
irradiated hot Jupiters.