A new model of the neutral gas torus of Europa

The neutral particles that escape the surface and exosphere of Europa populate a neutral gas torus around Jupiter. The detection and characterization of this neutral structure can not only shed light on the escape processes at work at Europa, but can also help to determine if Europa has a global influence on the Jovian plasma and magnetosphere.

We will present a new Monte Carlo model of the Europa neutral gas torus developed in the frame of the FACOM project funded by ANR (French national agency for research). Neutral ionization rates in the Jovian magnetosphere are computed based on Voyager plasma densities and temperatures, including suprathermal electrons. The source rate of neutrals escaping Europa’s gravity is constrained with the three-dimensional Exosphere Global Model EGM [Oza, Leblanc, et al., 2019]. In particular, we will present the first simulations of the H2O water torus of Europa, with a source rate of H2O at Europa constrained with EGM.

Finally, we will use our new model to reconsider the observability of the neutral torus in UV observations [Roth et al., 2023], energetic ion pitch angle distributions [Sarkango et al., 2023], ENA imaging [Smith et al., 2019], and pick-up ion observations [e.g. Szalay et al., 2022]. The impact of our results on future JUICE and Clipper observations of the Europa neutral gas torus will be presented.

This research holds as part of the project FACOM (ANR-22-CE49-0005-01_ACT) and has benefited from a funding provided by l’Agence Nationale de la Recherche (ANR) under the Generic Call for Proposals 2022. 

References:

Oza et al. 2019: 10.1016/j.pss.2019.01.006

Roth et al. 2023: 10.3847/PSJ/accddd

Sarkango et al. 2023: 10.1029/2023GL104374

Smith et al. 2019: 10.3847/1538-4357/aaed38

Szalay et al. 2022: 10.1029/2022GL098111

Smith, H. T., Mitchell, D. G., Johnson, R. E., Mauk, B. H., & Smith, J. E. (2019). Europa neutral torus confirmation and characterization based on observations and modeling. The Astrophysical Journal, 871(1), 69.