Precipitating electron properties of Ganymede’s aurora retrieved from Juno/UVS observations during PJ34
Year: 2025
Type: article
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.
Source: Astronomy and Astrophysics
Institutions: Centre National de la Recherche Scientifique, University of Liège, Aix-Marseille Université, University of Bern, University of Edinburgh, Université de Versailles Saint-Quentin-en-Yvelines, Sorbonne Université, Laboratoire atmosphères, milieux, observations spatiales, University of Michigan, Southwest Research Institute, Physique des interactions ioniques et moléculaires, Université Paris Cité, Université Paris Sciences et Lettres, Observatoire de Paris, CY Cergy Paris Université, Institut de Planétologie et d'Astrophysique de Grenoble, Université Grenoble Alpes, Institute for Space Astrophysics and Planetology, National Institute for Astrophysics, Université Toulouse III - Paul Sabatier, Institut de Recherche en Astrophysique et Planétologie, University of Alabama, Langley Research Center, Science Systems and Applications (United States)
Language: English
Subfield: Astronomy and Astrophysics
Field: Physics and Astronomy
Domain: Physical Sciences
Open Access status: gold
Estimated APC paid: $1,865
OpenAlex ID: W4415353121