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Simulations of Electron Beam Interactions with Substellar Atmospheres

Presentation #627.15 in the session Planetary Atmospheres - Theory.

Published onApr 03, 2024
Simulations of Electron Beam Interactions with Substellar Atmospheres

The atmospheric evolution of planets and substellar objects is governed by thermospheric and exospheric conditions, which modulate atmospheric mass-loss processes. Electrons incident on predominantly hydrogen substellar atmospheres (produced via magnetospheric dynamics or potentially host-satellite interactions) can ionize H2, driving the formation of H3+. For gas giant planets in the Solar System, H3+ cools the upper atmosphere through its strong thermal infrared emission. This means that future observations of H3+ in extrasolar substellar atmospheres could serve as a powerful diagnostic of atmospheric structure and temperature. Furthermore, electron impact excitation of H2 can produce UV aurorae, and so the observation of such aurorae would provide evidence of electron precipitation. The discovery of radio aurorae in brown dwarf atmospheres demonstrates the presence of auroral processes beyond the Solar System, with UV, optical, and IR aurorae also theoretically predicted. Simulating the interactions of high energy electrons with substellar hydrogen dominated atmospheres is critical for guiding ongoing observational searches for multi-wavelength auroral features in exoplanetary atmospheres, and interpreting their results. In this work, we present initial results of a simulated electron beam interaction with various H2 atmospheres. As a first step, we focus on the ionization profile, which is needed to understand the atmospheric chemistry effects of the electron beam, including the formation of H3+. We consider electron beam interactions with atmospheres of both gas giant planets and brown dwarfs.

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