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Harrison Nicholls (he/him)

Graduate student

Research theme

  • Astronomy and astrophysics

Sub department

  • Atmospheric, Oceanic and Planetary Physics

Research groups

  • Planetary Climate Dynamics
harrison.nicholls@physics.ox.ac.uk
Atmospheric Physics Clarendon Laboratory, room 113
nichollsh.github.io
  • About
  • Publications

Temperature–chemistry coupling in the evolution of gas giant atmospheres driven by stellar flares

Monthly Notices of the Royal Astronomical Society Oxford University Press 523:4 (2023) 5681-5702

Authors:

Harrison Nicholls, Olivia Venot

Abstract:

The effect of enhanced UV irradiation associated with stellar flares on the atmospheric composition and temperature of gas giant exoplanets was investigated. This was done using a 1D radiative-convective-chemical model with self-consistent feedback between the temperature and the non-equilibrium chemistry. It was found that flare-driven changes to chemical composition and temperature give rise to prolonged trends in evolution across a broad range of pressure levels and species. Allowing feedback between chemistry and temperature plays an important role in establishing the quiescent structure of these atmospheres, and determines their evolution due to flares. It was found that cooler planets are more susceptible to flares than warmer ones, seeing larger changes in composition and temperature, and that temperature–chemistry feedback modifies their evolution. Long-term exposure to flares changes the transmission spectra of gas giant atmospheres; these changes differed when the temperature structure was allowed to evolve self-consistently with the chemistry. Changes in spectral features due to the effects of flares on these atmospheres can be associated with changes in composition. The effects of flares on the atmospheres of sufficiently cool planets will impact observations made with JWST. It is necessary to use self-consistent models of temperature and chemistry in order to accurately capture the effects of flares on features in the transmission spectra of cooler gas giants, but this depends heavily on the radiation environment of the planet.
More details from the publisher
Details from ORA
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AGNI: A radiative-convective model for lava planet atmospheres

ArXiv 2506.00091 (2025)

Authors:

Harrison Nicholls, Raymond Pierrehumbert, Tim Lichtenberg
Details from ArXiV

AGNI: A radiative-convective model for lava planet atmospheres

Journal of Open Source Software The Open Journal 10:109 (2025) 7726-7726

Authors:

Harrison Nicholls, Raymond Pierrehumbert, Tim Lichtenberg
More details from the publisher

Absence of a Runaway Greenhouse Limit on Lava Planets

ArXiv 2505.11149 (2025)

Authors:

Iris D Boer, Harrison Nicholls, Tim Lichtenberg
Details from ArXiV

Self-limited tidal heating and prolonged magma oceans in the L 98-59 system

(2025)

Authors:

Harrison Nicholls, Claire Marie Guimond, Hamish CFC Hay, Richard D Chatterjee, Tim Lichtenberg, Raymond T Pierrehumbert
Details from ArXiV

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