Short‐term variability of Jupiter's satellite footprints as spotted by JWST

Knowles, K. L. ORCID: https://orcid.org/0000-0001-5055-8115, Melin, H. ORCID: https://orcid.org/0000-0001-5971-2633, Stallard, T. S. ORCID: https://orcid.org/0000-0003-3990-670X, Moore, L. ORCID: https://orcid.org/0000-0003-4481-9862, O'Donoghue, J. ORCID: https://orcid.org/0000-0002-4218-1191, Schmidt, C. ORCID: https://orcid.org/0000-0002-6917-3458, Szalay, J. R. ORCID: https://orcid.org/0000-0003-2685-9801, Tiranti, P. I. ORCID: https://orcid.org/0000-0001-7339-9495, Roberts, K. ORCID: https://orcid.org/0000-0002-5753-1262, Johnson, R. E. ORCID: https://orcid.org/0000-0003-4696-2160 and Thomas, E. M. ORCID: https://orcid.org/0000-0002-5773-6110 (2026) Short‐term variability of Jupiter's satellite footprints as spotted by JWST. Geophysical Research Letters, 53 (5). e2025GL118553. ISSN 1944-8007 doi: 10.1029/2025gl118553

Abstract/Summary

We present the main Alfvén wing (MAW) spots of Io and Europa as observed by the Near‐ Infrared Spectrograph onboard the James Webb Space Telescope. These auroral footprint features have been measured previously, but only in emission. Here, the derived ionospheric H+ 3 emission, temperature and column density are reported, as well as CH4 spectral radiance. At the Io footprint, H+ 3 temperatures are 670–900 K, excluding a spatially confined cold structure (538 ± 17 K), localized to the MAW spot, with high densities (0.98 ± 0.43 × 1016 m− 2). There are suggestions of a similar, less extreme H+ 3 population associated with the Europa footprint. However, temperatures at Io's MAW spot show significant variability within different observational exposures, indicating precipitation energy changes, sampling various regions of the ionosphere's altitudinal temperature profile. This work provides a new window into understanding the auroral processes driven by moon‐magnetosphere interactions in the Jovian system.

Item Type	Article
URI	https://centaur.reading.ac.uk/id/eprint/129072
Identification Number/DOI	10.1029/2025gl118553
Refereed	Yes
Divisions	Science > School of Mathematical, Physical and Computational Sciences > Department of Meteorology
Publisher	American Geophysical Union (AGU)
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