Increased Heat Transport in Ultra-Hot Jupiter Atmospheres Through H$_2$ Dissociation/Recombination [EPA]

http://arxiv.org/abs/1802.07725


A new class of exoplanets is beginning to emerge: planets whose dayside atmospheres more closely resemble stellar atmospheres as most of their molecular constituents dissociate. The effects of the dissociation of these species will be varied and must be carefully accounted for. Here we take the first steps towards understanding the thermodynamical consequences of dissociation and recombination of molecular hydrogen (H$_2$). Using a simple energy balance model with eastward winds, we demonstrate that H$_2$ dissociation/recombination can significantly increase the day-night heat transport on ultra-hot Jupiters: gas giant exoplanets where the temperature is $\gtrsim$ 2200 K somewhere on the planet. For these planets, significant H$_2$ dissociation should occur on their highly irradiated daysides, transporting some of the energy deposited on the dayside towards the nightside of the planet where the H atoms recombine into H$_2$; this mechanism bears similarities to latent heat. Given a fixed wind speed, this will act to increase the heat recirculation efficiency; alternatively, a measured heat recirculation efficiency will require slower wind speeds after accounting for H$_2$ dissociation/recombination.

Read this paper on arXiv…

T. Bell and N. Cowan
Fri, 23 Feb 18
26/64

Comments: 8 pages, 5 figures, submitted to ApJL, comments welcome