Idealised simulations of the deep atmosphere of hot Jupiters

Abstract

Context. The anomalously large radii of hot Jupiters has long been a mystery. However, by combining both theoretical arguments and 2D models, a recent study has suggested that the vertical advection of potential temperature leads to a hotter adiabatic temperature profile in the deep atmosphere than the profile obtained with standard 1D models. Aims. In order to confirm the viability of that scenario, we extend this investigation to 3D, time-dependent models. Methods. We use a 3D general circulation model DYNAMICO to perform a series of calculations designed to explore the formation and structure of the driving atmospheric circulations, and detail how it responds to changes in both the upper and deep atmospheric forcing.Results. In agreement with the previous, 2D study, we find that a hot adiabat is the natural outcome of the long-term evolution of the deep atmosphere. Integration times of the order of 1500 yr are needed for that adiabat to emerge from an isothermal atmosphere, explaining why it has not been found in previous hot Jupiter studies. Models initialised from a hotter deep atmosphere tend to evolve faster toward the same final state. We also find that the deep adiabat is stable against low-levels of deep heating and cooling, as long as the Newtonian cooling timescale is longer than ∼3000 yr at 200 bar. Conclusions. We conclude that steady-state vertical advection of potential temperature by deep atmospheric circulations constitutes a robust mechanism to explain the inflated radii of hot Jupiters. We suggest that future models of hot Jupiters be evolved for a longer time than currently done, and when possible that models initialised with a hot deep adiabat be included. We stress that this mechanism stems from the advection of entropy by irradiation-induced mass flows and does not require a (finely tuned) dissipative process, in contrast with most previously suggested scenarios.

Reinflation of Warm and Hot Jupiters

“…The heating rate is taken from Equation (34) of Thorngren & Fortney (2018) and is Gaussian with a peak at an equilibrium temperature of ∼ 1600 K. We find that the dependence of the inferred heating power with incident flux for the full hot Jupiter sample is consistent with both main-sequence re-inflation of hot Jupiters and post-main-sequence re-inflation of warm Jupiters. consistent with the expectation from simulations of the atmospheric dynamics of hot Jupiters that the deep atmosphere should be nearly adiabatic (Tremblin et al 2017, Sainsbury-Martinez et al 2019.…”

“…This irradiation leads to a slight increase in the radius relative to non-irradiated models, but when implemented in 1D structure models cannot explain the radius inflation of many hot Jupiters (Arras & Bildsten 2006, Fortney et al 2007). Irradiation powers atmospheric circulation that acts to transport heat both from day-to-night (Perez-Becker & Showman 2013, Komacek & Showman 2016) and vertically (Youdin & Mitchell 2010, Tremblin et al 2017, Zhang & Showman 2018, Komacek et al 2019, Sainsbury-Martinez et al 2019, but this is not included in our modeling framework. We model deposited heating as an additional term in the extra energy dissipation rate extra , as was done in previous studies of gaseous planet evolution with MESA (Wu & Lithwick 2013, Komacek & Youdin 2017, Millholland 2019.…”

“…The observation that many transiting hot Jupiters have radii larger than expected from standard evolutionary models is an outstanding question of exoplanetary science , Fortney et al 2010, Laughlin & Lissauer 2015, Laughlin 2018. A variety of mechanisms have been propsed to explain the anomalous transit radii of hot Jupiters (Weiss et al 2013, Baraffe et al 2014, including tidal mechanisms (Bodenheimer et al 2001, Gu et al 2003, 2004, Jackson et al 2008, Ibgui & Burrows 2009, Miller et al 2009, Arras & Socrates 2010, Ibgui et al 2010, Leconte et al 2010, Gu et al 2019, modifications to the microphysics of hot Jupiters (Burrows et al 2007, Chabrier & Baraffe 2007, Leconte & Chabrier 2012, Kurokawa & Inutsuka 2015, incident stellar-fluxdriven hydrodynamic mechanisms , Youdin & Mitchell 2010, Tremblin et al 2017, Sainsbury-Martinez et al 2019, and Ohmic dissipation (Batygin & Stevenson 2010, Perna et al 2010, Batygin et al 2011, Huang & Cumming 2012, Menou 2012, Rauscher & Menou 2013, Wu & Lithwick 2013, Rogers & Showman 2014, Rogers & Komacek 2014, Ginzburg & Sari 2016. Studies of the radius distribution of hot Jupiters (Demory & Seager 2011, Laughlin et al 2011, Miller & Fortney 2011...…”

Atmospheric circulation of brown dwarfs and directly imaged exoplanets driven by cloud radiative feedback: effects of rotation

“…The uncertainties in the bottom boundary conditions and the impacts on the general circulation have long been an issue for shallow models of gaseous planets (e.g., Showman et al 2020). Such issues have been shown for shallow models relevant to Jupiter (e.g., Schneider & Liu 2009) and to hot Jupiters (e.g., Mayne et al 2017;Sainsbury-Martinez et al 2019;Carone et al 2020).…”

Inflation of migrated hot Jupiters

“…of potential temperature (Tremblin et al 2017;Sainsbury-Martinez et al 2019). The second radiation dependent mechanism is Ohmic dissipation, in which electric currents move from the atmosphere to the interior (Batygin & Stevenson 2010;Perna et al 2010;Huang & Cumming 2012;Rauscher & Menou 2013;Wu & Lithwick 2013;Rogers & Showman 2014;Ginzburg & Sari 2016).…”