Lightning And Charge Processes In Brown Dwarf and Exoplanet Atmospheres

The study of the composition of brown dwarf atmospheres helped to understand their formation and evolution. Similarly, the study of exoplanet atmospheres is expected to constrain their formation and evolutionary states.

We use results from 3D simulations, kinetic cloud formation and kinetic ion-neutral chemistry to investigate ionisation processes which will affect their atmosphere chemistry: The dayside of super-hot Jupiters is dominated by atomic hydrogen, and not H2O. Such planetary atmospheres exhibit a substantial degree of thermal ionisation and clouds only form on the nightside where lightning leaves chemical tracers (e.g. HCN) for possibly long enough to be detectable. External radiation may cause exoplanets to be enshrouded in a shell of highly ionised, H+3-forming gas and a weather-driven aurora may emerge.

Brown dwarfs enable us to study the role of electron beams for the emergence of an extrasolar, weather-system driven aurora-like chemistry, and the effect of strong magnetic fields on cold atmospheric gases. Electron beams trigger the formation of H+3 in the upper atmosphere of a brown dwarf (e.g. LSR-J1835) which may react with it to form hydronium, H3O+, as a longer lived chemical tracer. Brown dwarfs and super-hot gas giants may be excellent candidates to search for H3O+ as an H+3 product.

Christiane Helling (1), Paul B Rimmer (2) ((1) Centre for Exoplanet Science, University of St Andrews & SRON Netherlands Institute for Space Research, (2) University of Cambridge, Cavendish Astrophysics & MRC Laboratory of Molecular Biology)
(Submitted on 11 Mar 2019)
Comments: 16 pages, accepted for publication in the Philosophical Transactions A of the Royal Society
Subjects: Earth and Planetary Astrophysics (astro-ph.EP); High Energy Astrophysical Phenomena (astro-ph.HE); Solar and Stellar Astrophysics (astro-ph.SR); Atmospheric and Oceanic Physics (physics.ao-ph); Space Physics (physics.space-ph)
DOI: 10.1098/rsta.2018.0398
Cite as: arXiv:1903.04565 [astro-ph.EP] (or arXiv:1903.04565v1 [astro-ph.EP] for this version)
Submission history
From: Christiane Helling
[v1] Mon, 11 Mar 2019 19:48:49 UTC (892 KB)
https://arxiv.org/abs/1903.04565
Astrobiology