Radiative Hydrodynamic Simulations of HD209458b: Temporal Variability

TL;DR

This paper introduces a comprehensive 3D simulation method for HD209458b's atmosphere, revealing temperature inversions, instabilities, and variability in temperature and hot spot location due to advanced radiative and dynamical modeling.

Contribution

The study develops a novel 3D radiative hydrodynamic simulation approach with improved energy coupling, opacities, and turbulence modeling for hot Jupiter atmospheres.

Findings

Temperature inversions at the sub-stellar point due to opacity and flow structure.

Atmospheric instabilities cause velocity and temperature fluctuations.

Hot spot location varies by over 20 degrees, showing dynamic atmospheric behavior.

Abstract

We present a new approach for simulating the atmospheric dynamics of the close-in giant planet HD209458b that allows for the decoupling of radiative and thermal energies, direct stellar heating of the interior, and the solution of the full 3D Navier Stokes equations. Simulations reveal two distinct temperature inversions (increasing temperature with decreasing pressure) at the sub-stellar point due to the combined effects of opacity and dynamical flow structure and exhibit instabilities leading to changing velocities and temperatures on the nightside for a range of viscosities. Imposed on the quasi-static background, temperature variations of up to 15% are seen near the terminators and the location of the coldest spot is seen to vary by more than 20 degrees, occasionally appearing west of the anti-solar point. Our new approach introduces four major improvements to our previous methods including simultaneously solving both the thermal energy and radiative equations in both the optical and infrared, incorporating updated opacities, including a more accurate treatment of stellar energy deposition that incorporates the opacity relevant for higher energy stellar photons, and the addition of explicit turbulent viscosity.