Auroral 3D structure retrieval from the Juno/UVS data

¹ Laboratory for Planetary and Atmospheric Physics, STAR Institute, University of Liège, Liège, Belgium
² The University of Edinburgh, School of GeoSciences, Edinburgh, UK
³ Aix-Marseille Université, CNRS, CNES, Institut Origines, LAM, Marseille, France
⁴ Space Science and Engineering Division, Southwest Research Institute, San Antonio, TX, USA
⁵ NASA Langley Research Center, Hampton, Va, USA
⁶ Science Systems And Applications Inc., Hampton, Va, USA
⁷ Univ. Grenoble Alpes, CNRS, IPAG, 38000 Grenoble, France
⁸ Univ. Grenoble Alpes, CSUG, 38000 Grenoble, France
⁹ Jet Propulsion Laboratory, California Institute of Technology, 4800 Oak Grove Drive, Pasadena, CA 91109, USA
¹⁰ Institute for Space Astrophysics and Planetology, National Institute for Astrophysics (INAF-IAPS), Roma, Italy
¹¹ Space Research Institute (IWF), Austrian Academy of Sciences (ÖAW) Schmiedlstraße 6, 8042 Graz, Austria

^★ Corresponding author; bilal.benmahi@uliege.be

Received: 9 July 2024
Accepted: 25 September 2024

Abstract

Context. Jovian auroras, the most powerful in the Solar System, result from the interaction between the magnetosphere and atmosphere of Jupiter. While the horizontal morphology of these phenomena has been widely studied, their vertical structure, determined by the penetration depth of the magnetospheric electron into the auroral regions, remains relatively unexplored. Previous observations, including those from the Hubble Space Telescope (HST), have addressed this question to a limited extent.

Aims. In this study we aim to map the vertical structure of Jovian auroral emissions.

Methods. Using observations from Juno’s UltraViolet Spectrograph (UVS), we examined the vertical structure of the auroral emissions. Building on a recent study of auroral energy mapping based on UVS observations that mapped the average energy of precipitating electrons in the Jovian auroral regions, we find a relationship between this average energy and the volume emission rate (VER) of H₂ for two types of electron energy distributions: monoenergetic and a kappa distribution with κ = 2.5.

Results. Using brightness maps, we derived the 3D VER structure of Jovian auroras in both northern and southern regions, across multiple spacecraft perijoves (PJs). By considering the example of PJ11, we find that the average altitude of the VER peak in the polar emission region is approximately ~250 km for the monoenergetic distribution case and ~190 km for kappa distribution case. In the main emission region, we find that the average altitude of the VER peak is approximately ~260 km for the case of monoenergetic distribution and ~197 km for kappa distribution case. For the other PJs, we obtained results that are very similar to those of PJ11.

Conclusions. Our findings are, on average, consistent with measurements from the Galileo probe and the HST observations. This study contributes to a better understanding of the complexity of Jovian auroras and highlights the importance of using Juno observations when probing their vertical structure. Considering the variability in the κ parameter in the auroral region, we also studied the impact of this variability on the vertical structure of the auroral emission. This sensitivity study reveals that the influence of the κ parameter on our results was very weak. However, the impact of the κ variability on the VER amplitude shows that there is an influence on the thermal structure and chemical composition of the atmosphere in the auroral regions.