On the Absorption and Redistribution of Energy in Irradiated Planets

TL;DR

This paper introduces simplified models for irradiated planet atmospheres to explore how energy absorption and redistribution affect observable features like eclipses and phase curves, providing insights into atmospheric temperature structures.

Contribution

The study develops coupled grey atmosphere toy models that self-consistently simulate energy absorption and redistribution, linking simplified parameters to complex radiative transfer results.

Findings

Energy redistribution influences temperature inversions.

Model parameters affect observable phase curves.

Temperature inversions can occur at moderate optical depths.

Abstract

We present a sequence of toy models for irradiated planet atmospheres, in which the effects of geometry and energy redistribution are modelled self-consistently. We use separate but coupled grey atmosphere models to treat the ingoing stellar irradiation and outgoing planetary reradiation. We investigate how observed quantities such as full phase secondary eclipses and orbital phase curves depend on various important parameters, such as the depth at which irradiation is absorbed and the depth at which energy is redistributed. We also compare our results to the more detailed radiative transfer models in the literature, in order to understand how those map onto the toy model parameter space. Such an approach can prove complementary to more detailed calculations, in that they demonstrate, in a simple way, how the solutions change depending on where, and how, energy redistribution occurs. As an example of the value of such models, we demonstrate how energy redistribution and temperature equilibration at moderate optical depths can lead to temperature inversions in the planetary atmosphere, which may be of some relevance to recent observational findings.