Precipitating electron properties of Ganymede’s aurora retrieved from Juno/UVS observations during PJ34

Context . Ganymede’s UV aurorae, observed by HST and Juno/UVS, trace interactions between its atmosphere and Jupiter’s magneto-sphere. These emissions, dominated by O I lines at 130.4 and 135.6 nm, are driven by electron impact on species such as H 2 O, O, and O 2 , and yet the properties of the precipitating electrons remain poorly constrained. Aims . Our aim was to retrieve the energy and flux of precipitating electrons using UV observations from Juno/UVS during PJ34 and to assess the dominant atmospheric species producing the observed emissions. Methods . Using the TransPlanet electron transport model and a non-local thermodynamic equilibrium (non-LTE) radiative transfer module, we simulated O I emissions for 17 auroral subregions, testing both monoenergetic and kappa-type electron distributions. The I (135.6 nm)/ I (130.4 nm) line ratio was used as a diagnostic, with values varying by target species. Results . Monoenergetic distributions fit most regions better, with mean energies of 17–300 eV and fluxes up to 2 mW m −2 . Kappa and Maxwellian distributions yielded higher fluxes, but poorer spectral fits. Poor fits in some regions reflect low S/N or non-ideal electron populations. Conclusions . Our results suggest that Ganymede’s UV aurorae are mainly driven by low- to intermediate-energy electrons. Upcoming high-resolution observations and in situ data from Juice and Europa Clipper will be key to refining these diagnostics.

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Publication Details

Journal
Astronomy and Astrophysics
Published
2025-10-20
DOI
https://doi.org/10.1051/0004-6361/202556996
Citations
2
Primary Topic
Astro and Planetary Science
Type
article
Field-Weighted Citation Impact
2.31
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article

Precipitating electron properties of Ganymede’s aurora retrieved from Juno/UVS observations during PJ34

J. H. Waite, T. Greathouse, Michel Blanc, Alexis Bouquet et al.
2 citations
Astronomy and Astrophysics
Astro and Planetary Science
2.31
article

Precipitating electron properties of Ganymede’s aurora retrieved from Juno/UVS observations during PJ34

J. H. Waite, T. Greathouse, Michel Blanc, Alexis Bouquet, V. Hue, Philippa Molyneux, Guillaume Gronoff, Rohini Giles, B. Collet, G. R. Gladstone, Bertrand Bonfond, Alessandro Moirano, Denis Grodent, Corentin Louis, Xianzhe Jia, Bilal Benmahi, François Leblanc, Benjamin Benne, Benoît Hubert, M. Barthélémy, A. Vorbuger
article en
2 citations

Abstract

Context . Ganymede’s UV aurorae, observed by HST and Juno/UVS, trace interactions between its atmosphere and Jupiter’s magneto-sphere. These emissions, dominated by O I lines at 130.4 and 135.6 nm, are driven by electron impact on species such as H 2 O, O, and O 2 , and yet the properties of the precipitating electrons remain poorly constrained. Aims . Our aim was to retrieve the energy and flux of precipitating electrons using UV observations from Juno/UVS during PJ34 and to assess the dominant atmospheric species producing the observed emissions. Methods . Using the TransPlanet electron transport model and a non-local thermodynamic equilibrium (non-LTE) radiative transfer module, we simulated O I emissions for 17 auroral subregions, testing both monoenergetic and kappa-type electron distributions. The I (135.6 nm)/ I (130.4 nm) line ratio was used as a diagnostic, with values varying by target species. Results . Monoenergetic distributions fit most regions better, with mean energies of 17–300 eV and fluxes up to 2 mW m −2 . Kappa and Maxwellian distributions yielded higher fluxes, but poorer spectral fits. Poor fits in some regions reflect low S/N or non-ideal electron populations. Conclusions . Our results suggest that Ganymede’s UV aurorae are mainly driven by low- to intermediate-energy electrons. Upcoming high-resolution observations and in situ data from Juice and Europa Clipper will be key to refining these diagnostics.

Astronomy and AstrophysicsVol. 703
Southwest Research Institute (US), Centre National de la Recherche Scientifique (FR), Planetary Science Institute (US), Langley Research Center (US), Université Toulouse III - Paul Sabatier (FR), University of Alabama (US), Université de Versailles Saint-Quentin-en-Yvelines (FR), Université Paris Cité (FR), Aix-Marseille Université (FR), University of Michigan (US), NASA Exoplanet Science Institute (US), Sorbonne Université (FR), Sorbonne Paris Cité (FR), Institute for Space Astrophysics and Planetology (IT), Institut de Neurosciences des Systèmes (FR), Science Systems and Applications (United States) (US), Centre de Géosciences (FR), Laboratoire atmosphères, milieux, observations spatiales (FR), Physique des interactions ioniques et moléculaires (FR), Université Grenoble Alpes (FR), University of Edinburgh (GB)
Openalex Percentile: Top 10%
Astro and Planetary Science
2.31
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