Properties of Electrons Accelerated by the Ganymede‐Magnetosphere Interaction: Survey of Juno High‐Latitude Observations

• Published in: Journal of geophysical research. Space physics 2024-05, Vol.129 (5), p.n/a
• Main Authors: Rabia, J., Hue, V., André, N., Nénon, Q., Szalay, J. R., Allegrini, F., Sulaiman, A. H., Louis, C. K., Greathouse, T. K., Sarkango, Y., Santos‐Costa, D., Blanc, M., Penou, E., Louarn, P., Ebert, R. W., Gladstone, G. R., Mura, A., Connerney, J. E. P., Bolton, S. J.
• Format: Article
• Language: English
• Subjects: Atmosphere; Auroral emissions; Broadband; Charged particles; Electromagnetic radiation; Electron beams; Electron energy; Electrons; Emissions; Energy flux; Europa; Galilean satellites; Ganymede; Hubble Space Telescope; Jupiter; Jupiter atmosphere; Jupiter probes; Jupiter satellites; Magnetic fields; Magnetic properties; Moon; Moons; Particle acceleration; Particle interactions; Particle physics; Planetary magnetospheres; Plasma; Rotating plasmas; Space telescopes; Spacecraft; Statistical methods; Tracing; Volcanic activity
• ISSN: 2169-9380; 2169-9402
• DOI: 10.1029/2024JA032604

The encounter between the Jovian co‐rotating plasma and Ganymede gives rise to electromagnetic waves that propagate along the magnetic field lines and accelerate particles by resonant or non‐resonant wave‐particle interaction. They ultimately precipitate into Jupiter's atmosphere and trigger auroral emissions. In this study, we use Juno/JADE, Juno/UVS data, and magnetic field line tracing to characterize the properties of electrons accelerated by the Ganymede‐magnetosphere interaction in the far‐field region. We show that the precipitating energy flux exhibits an exponential decay as a function of downtail distance from the moon, with an e‐folding value of 29°, consistent with previous UV observations from the Hubble Space Telescope (HST). We characterize the electron energy distributions and show that two distributions exist. Electrons creating the Main Alfvén Wing (MAW) spot and the auroral tail always have broadband distribution and a mean characteristic energy of 2.2 keV while in the region connected to the Transhemispheric Electron Beam (TEB) spot the electrons are distributed non‐monotonically, with a higher characteristic energy above 10 keV. Based on the observation of bidirectional electron beams, we suggest that Juno was located within the acceleration region during the 11 observations reported. We thus estimate that the acceleration region is extended, at least, between an altitude of 0.5 and 1.3 Jupiter radius above the 1‐bar surface. Finally, we estimate the size of the interaction region in the Ganymede orbital plane using far‐field measurements. These observations provide important insights for the study of particle acceleration processes involved in moon‐magnetosphere interactions. Plain Language Summary The Galilean moons orbit in a plasma‐rich environment, created by the intense volcanism of Io and transported radially outward in the Jovian magnetosphere. At the orbital locations of the moons, this plasma, co‐rotating with Jupiter, flows at a velocity significantly higher than the moons' orbital speed. Consequently, the moons disturb the plasma flow. This interaction gives rise to a set of physical processes, including the generation of electromagnetic waves that propagate away from the moons and accelerate charged particles, triggering auroral emissions by precipitating into Jupiter's atmosphere. In this study, we investigate the properties of the electrons accelerated by the Ganymede‐magnetosphere interaction. We use data from the JADE