Electron Beams at Europa

• Published in: Geophysical research letters 2024-07, Vol.51 (13), p.n/a
• Main Authors: Allegrini, F., Saur, J., Szalay, J. R., Ebert, R. W., Kurth, W. S., Cervantes, S., Smith, H. T., Bagenal, F., Bolton, S. J., Clark, G., Connerney, J. E. P., Louarn, P., Mauk, B., McComas, D. J., Pontoni, A., Sarkango, Y., Valek, P., Wilson, R. J.
• Format: Article
• Language: English
• Subjects: Aerospace environments; Atmosphere; Electromagnetic induction; Electromagnetic soundings; electron; Electron beams; Electrons; Europa; flyby; Flyby missions; Icy satellites; Ionization; Ionosphere; Juno; Jupiter; Jupiter probes; Jupiter satellites; Jupiter's magnetosphere; Magnetic field; Magnetic fields; Magnetic induction; Moon; Oceans; Planetary magnetic fields; Plasma; Satellite atmospheres; Space missions; Space plasmas; Spacecraft; Spacecraft power supplies
• ISSN: 0094-8276; 1944-8007
• DOI: 10.1029/2024GL108422

Jupiter's moon Europa contains a subsurface ocean whose presence is inferred from magnetic field measurements, the interpretation of which depends on knowledge of Europa's local plasma environment. A recent Juno spacecraft flyby returned new observations of plasma electrons with unprecedented resolution. Specifically, powerful magnetic field‐aligned electron beams were discovered near Europa. These beams, with energies from ∼30 to ∼300 eV, locally enhance electron‐impact‐excited emissions and ionization in Europa's atmosphere by more than a factor three over the local space environment, and are associated with large jumps of the magnetic fields. The beams therefore play an essential role in shaping Europa's plasma and magnetic field environment and thus need to be accounted for electromagnetic sounding of Europa's ocean and plume detection by future missions such as JUICE and Europa Clipper. Plain Language Summary A recent Juno spacecraft close flyby of Jupiter's moon Europa revealed the presence of powerful electrons beams. Based on previous observations and modeling of electron beams at the moon Io, such beams were not expected to be observed so close to Europa. Overall, the proximity of the beams to Europa indicates that the acceleration of these electrons takes place much closer to Europa than anticipated and that these beams, therefore, stem from a new and previously unknown acceleration mechanism. The beams are predicted to have an outsized influence on the ionization of the constituents of Europa's tenuous atmosphere and are accompanied with large magnetic field perturbations. Hence, these electron beams are an important ionization source that modify the moon's ionosphere, the electric current systems, and the magnetic field environment. In particular, the presence of electron beams will affect plasma conditions that are used to infer the extent of a subsurface ocean via the magnetic induction signal. These beams significantly impact the space plasma environment around Europa which needs to be accounted for by future missions such as ESA's (European Space Agency) JUICE (Jupiter Icy Moons Explorer) and NASA's (National Aeronautics and Space Administration) Europa Clipper mission. Key Points Powerful electron beams that significantly shape Europa's space environment are discovered during a Juno flyby The beams enhance electron‐impact‐excited emissions in Europa's atmosphere and are associated with large jumps of the magnetic fields The beams' proximit