Probing H3+ emission spectra in the footprints of Galilean moons with JIRAM

Since the discovery of Jupiter’s auroral footprints linked to the Galilean moons - Io, Europa, Ganymede, and Callisto - extensive efforts have been made to unravel the mechanisms behind these unique phenomena, which have no equivalent on Earth. The Juno mission has been fundamental in this effort, providing unprecedented access to Jupiter's polar regions, significantly enhancing our understanding of the satellite footprints and Jovian aurorae. Juno’s observations have revealed exceptional detail, enabling a more thorough characterization of the morphology of the footprints and the electrodynamic processes that drive their formation.

In this study, we aim to investigate these features from a new perspective by examining their spectral signature, a dimension largely unexplored until now, with a focus on the H₃⁺ emissions in the infrared. This is accomplished by combining the L-band images and spectra acquired from orbit PJ 1 to 40 by the Jovian InfraRed Auroral Mapper (JIRAM), onboard of the Juno spacecraft. The images provide the spatial context necessary to identify the spectra sampling Io-, Europa- and Ganymede-induced aurorae, the primary targets of this work. These spectra are then used to derive the temperature and column density of H₃⁺ within the various structures forming the footprints, including the Main Alfvén Wing (MAW), the Transhemispheric Electron Beam (TEB), the Reflected Alfvén Wing (RAW). Additionally, we compare the derived values with those of the main aurora, as reported in earlier JIRAM spectral studies, to gain a deeper understanding of the similarities and differences between the footprints and the main emission.

Through this analysis, our objective is to provide further insights to the existing body of knowledge on Jovian auroral footprints and on the complex interactions among Jupiter's magnetosphere, ionosphere, and its moons.