The Inhomogeneity Effect: Unveiling the Overlooked Roles of Weather on the Evolution of Hot Jupiters

One-dimensional (1D) models have long been the cornerstone for understanding planetary evolution, but they fall short in capturing the complex, inherently three-dimensional (3D) and spatially diverse nature of these bodies. Here we proposed a general principle that spatial inhomogeneities and temporal variations in a planet’s surface and atmosphere significantly enhance its cooling, emphasizing the critical role of their orbital and rotational configurations. The inhomogeneity effect has strong implications on the cooling of inflated hot Jupiters and the interpretation of their bloated sizes. Using a state-of-the-art non-hydrostatic general circulation model, we simulated the atmospheric dynamics and vertical heat flow of hot Jupiters. We show that the planetary cooling flux increases with atmospheric drag due to increased day–night contrast and spatial inhomogeneity. The temperature dependence of the infrared opacity greatly amplifies the opacity inhomogeneity. Although atmospheric circulation could transport heat downward in a narrow region above the radiative-convective boundary, the opacity inhomogeneity effect overcomes the dynamical effect and leads to a larger overall interior cooling than the local simulations. In a strong-drag atmosphere hotter than 1600 K, a significant inhomogeneity effect in 3D models can boost interior cooling several-fold compared to the 1D models. Our findings contest an existing view of atmospheric circulation as the primary inflation mechanism of hot Jupiters. But it also highlights the intricate relationship between a planet’s interior and its atmosphere: the interior flux of a giant planet impacts atmospheric motion, and the atmosphere dictates the interior’s cooling. Our research underscores the necessity of 3D atmospheric models for a comprehensive understanding of giant planet evolution, especially in the JWST era. Future studies on the inflation mechanisms of hot Jupiters must incorporate these complex 3D atmospheric structures, paving the way for a deeper understanding of origin and evolution of giant planets.

References:

Zhang, X., 2023a, The Inhomogeneity Effect I: Inhomogeneous Surface and Atmosphere Accelerate Planetary Cooling, ApJ, 957, 20.

Zhang, X., 2023b, The Inhomogeneity Effect II: Rotational and Orbital States Impact Planetary Cooling, ApJ, 957, 21.

Zhang, X., Li, C., Ge, H., and Le, T., 2023c, The Inhomogeneity Effect III: Weather Impacts on the Heat flow of Hot Jupiters, ApJ, 957, 22.