Europa's Influence on the Jovian Energetic Electron Environment as Observed by Juno's Micro Advanced Stellar Compass

• Published in: Geophysical research letters 2024-05, Vol.51 (9), p.n/a
• Main Authors: Herceg, M., Jørgensen, J. L., Denver, T., Jørgensen, P. S., Benn, M., Connerney, J. E. P., Fléron, R., Mauk, B., Bolton, S. J.
• Format: Article
• Language: English
• Subjects: Attitudes; Cameras; Compasses; Electron flux; Electrons; Energy; Europa; Galilean satellites; Jupiter; Jupiter probes; Jupiter satellites; Moon; Orbit insertion; Particle physics; Pitch (inclination); Planetary magnetospheres; Protons; Shielding; Signatures; Surveys; Upstream
• ISSN: 0094-8276; 1944-8007
• DOI: 10.1029/2023GL104685

The micro Advanced Stellar Compass is an attitude reference for the MAG investigation onboard Juno. The μASC camera head unit images the star field with a CCD that is also sensitive to particles with enough energy to pass through the camera shielding: >15 MeV electrons and >80 MeV protons. This provides the capability to monitor fluxes of high‐energy particles in Jupiter’s magnetosphere. A survey of energetic electron fluxes sampled during the first 47 Juno orbits reveals instances of variations observed when Juno is traversing the M‐shell of the Galilean moons. Juno's traversal of the Europa M‐shell often results in distinctly particle signatures. We present the μASC observations of increased electron flux during the crossing of Europa’s plasma wake, and depletion of energetic electron flux on the upstream side. The upstream/downstream differences indicate that the wake environment of Europa drives strong pitch angle scattering on relativistic electrons. Plain Language Summary The attitude reference (μASC) used for the MAG investigation onboard Juno is also sensitive to particles with enough energy to pass through the camera shielding. This provides the capability to monitor fluxes of high‐energy particles in Jupiter’s magnetosphere, as the Juno has done since orbit insertion. A μASC survey of electron fluxes reveals instances of variations observed when Juno is traversing the M‐shell of Jupiter’s moon Europa. We present particle signatures related to the interaction with Europa and discuss the implications. Key Points Europa’s wake affects the high‐energy electron driftshell by scattering electrons into the loss‐cone Increase in e− flux is around x2.3 at distances ∼30 RE, and is gradually dissolved as far as 20° downstream Europa will stop the energetic electron drift shells and will be mostly free from hard radiation on the leading side