Analytical Models of Exoplanetary Atmospheres. V. Non-gray Thermal Structure with Coherent Scattering

TL;DR

This paper models the thermal structure of irradiated exoplanetary atmospheres considering spectral lines with different formation processes, revealing how absorption and scattering influence temperature profiles and greenhouse effects.

Contribution

It introduces a non-gray model incorporating coherent scattering effects in spectral lines, advancing understanding of atmospheric thermal structures.

Findings

Pure absorption lines cool surface layers.

Pure scattering lines prevent surface cooling.

Coherent scattering causes anti-greenhouse and greenhouse effects.

Abstract

We apply the picket fence treatment to model the effects brought about by spectral lines on the thermal structure of irradiated atmospheres. The lines may be due to purely absorption processes, purely coherent scattering processes or some combination of absorption and scattering. If the lines arise as a pure absorption process, the surface layers of the atmosphere are cooler whereas this surface cooling is completely absent if the lines are due to pure coherent isotropic scattering. The lines also lead to a warming of the deeper atmosphere. The warming of the deeper layers is, however, independent of the nature of line formation. Accounting for coherent isotropic scattering in the shortwave and longwave continuum results in anti-greenhouse cooling and greenhouse warming on an atmosphere-wide scale. The effects of coherent isotropic scattering in the line and continuum operate in tandem to determine the resulting thermal structure of the irradiated atmosphere.