Rosalba Perna, Kevin Heng, Frederic Pont
Hot Jupiters, due to the proximity to their parent stars, are subjected to a
strong irradiating flux which governs their radiative and dynamical properties.
We compute a suite of 3D circulation models with dual-band radiative transfer,
exploring a relevant range of irradiation temperatures (770K <~ Tirr <~ 3000K),
both with and without temperature inversions. We find that, for irradiation
temperatures Tirr <~ 2000K, heat redistribution is very efficient, producing
comparable day- and night-side fluxes. For Tirr ~ 2200-2400K, redistribution
starts to break down, resulting in a high day-night flux contrast. Our
simulations support the physical intuition that the efficiency of heat transfer
is primarily governed by the ratio of advective to radiative timescales. For
the same Tirr, models with temperature inversions display a higher day-night
contrast, but we find this opacity-driven effect to be secondary to
irradiation. The hotspot offset from the substellar point is large when
insolation is weak and redistribution is efficient, and decreases as
redistribution breaks down. We further explore the importance of various
dissipation mechanisms with the strength of the irradiating flux. The
atmospheric flow can be potentially subjected to the Kelvin-Helmholtz
instability only in the uppermost layers, with a depth that penetrates to
pressures of a few millibars at most. Shocks penetrate deeper, down to several
bars in the hottest model. For a B ~ a few Gauss, Ohmic dissipation generally
occurs down to deeper levels than shock dissipation (to tens of bars), but the
penetration depth varies with the atmospheric opacity. The total dissipated
Ohmic power increases steeply with the strength of the irradiating flux and the
dissipation depth recedes into the atmosphere, favoring radius inflation in the
most irradiated objects. (Abridged)
View original:
http://arxiv.org/abs/1201.5391
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