Hydrodynamic Simulations of Unevenly Irradiated Jovian Planets

摘要

We employ a two-dimensional grid-based hydrodynamic model to simulate upperatmospheric dynamics on extrasolar giant planets. Our model is well-suited tosimulate the dynamics of the atmospheres of planets with high orbitaleccentricity that are subject to widely-varying irradiation conditions. Weidentify six such planets, with eccentricities between $e=0.28$ and $e=0.93$and semimajor axes ranging from $a=0.0508$ A.U. to $a=0.432$ A.U., asparticularly interesting objects for study. For each of these planets, wedetermine the temperature profile and resulting infrared light curves in the8-$\mu$m Spitzer bands. Especially notable are the results for HD 80606b, whichhas the largest eccentricity ($e=0.9321$) of any known planet, and HAT-P-2b,which transits its parent star, so that its physical properties arewell-constrained. Despite the variety of orbital parameters, the atmosphericdynamics of these eccentric planets display a number of interesting commonproperties. In all cases, the atmospheric response is primarily driven by theintense irradiation at periastron. The resulting expansion of heated airproduces high-velocity turbulent flow, including long-lived circumpolarvortices. Additionally, a superrotating acoustic front develops on someplanets; the strength of this disturbance depends on both the eccentricity andthe temperature gradient resulting from uneven heating. The specifics of theresulting infrared light curves depend strongly on the orbital geometry. Weshow, however, that the variations on HD 80606 b and HAT-P-2b should be readilydetectable at 4.5 and 8 $\mu$m using the Spitzer Space Telescope. Indeed, thesetwo objects present the most attractive observational targets of all knownhigh-$e$ exoplanets.