| Issue |
A&A
Volume 706, February 2026
|
|
|---|---|---|
| Article Number | L16 | |
| Number of page(s) | 4 | |
| Section | Letters to the Editor | |
| DOI | https://doi.org/10.1051/0004-6361/202558379 | |
| Published online | 18 February 2026 | |
Letter to the Editor
Juno’s high-spatial-resolution ultraviolet observations of Ganymede’s auroral patches
Constraints on the magnetospheric source region
1
Laboratory for Planetary and Atmospheric Physics, STAR Institute, University of Liège Liège, Belgium
2
Institute for Space Astrophysics and Planetology, National Institute for Astrophysics (INAF-IAPS) Rome, Italy
3
Institute of Geophysics and Meteorology, University of Cologne Cologne, Germany
4
Department of Earth & Planetary Sciences, University of Hong Kong Hong Kong, China
5
Aix-Marseille Université, CNRS, CNES, Institut Origines, LAM Marseille, France
6
Space Science Division, Southwest Research Institute San Antonio TX, USA
★ Corresponding author: This email address is being protected from spambots. You need JavaScript enabled to view it.
Received:
3
December
2025
Accepted:
20
January
2026
Aims. We analyzed ultraviolet observations of Ganymede recorded on June 7, 2021, by the Juno spacecraft, which observed the aurora at high spatial resolution in order to detect the presence of auroral sub-structures. The emission mainly comes from two oxygen lines at 130.4 and 135.6 nm, which are excited under electron precipitation.
Methods. We produced longitude–latitude projections of the oxygen emission lines from Ganymede’s atmosphere to investigate the presence of small-scale auroral features. We adopted a magnetic field model of Ganymede’s magnetosphere to map between the moon surface and the surrounding space, in order to determine the regions magnetically connected to the aurora.
Results. We find auroral patches on the leading, downstream side of Ganymede. Their typical size is ∼50 km, and they have a brightness of up to ∼200 Rayleigh. These features map approximately to the downstream reconnection region and seemingly resemble the terrestrial and Jovian mesoscale auroras associated with sub-storms and dawn storms, respectively. This could indicate that magnetospheres of celestial bodies host similar physical process(es) despite their different conditions and dynamics.
Key words: planets and satellites: aurorae / planets and satellites: magnetic fields
© The Authors 2026
Open Access article, published by EDP Sciences, under the terms of the Creative Commons Attribution License (https://creativecommons.org/licenses/by/4.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.
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