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- Title
Evidence for Non‐Monotonic and Broadband Electron Distributions in the Europa Footprint Tail Revealed by Juno In Situ Measurements.
- Authors
Rabia, J.; Hue, V.; Szalay, J. R.; André, N.; Nénon, Q.; Blanc, M.; Allegrini, F.; Bolton, S. J.; Connerney, J. E. P.; Ebert, R. W.; Gladstone, G. R.; Greathouse, T. K.; Louarn, P.; Mura, A.; Penou, E.; Sulaiman, A. H.
- Abstract
We characterize the precipitating electrons accelerated in the Europa‐magnetosphere interaction by analyzing in situ measurements and remote sensing observations recorded during 10 crossings of the flux tubes connected to Europa's auroral footprint tail by Juno. The electron downward energy flux, ranging from 34 to 0.8 mW/m2, exhibits an exponential decay as a function of downtail distance, with an e‐folding factor of 7.4°. Electrons are accelerated at energies between 0.3 and 25 keV, with a characteristic energy that decreases downtail. The electron distributions form non‐monotonic spectra in the near tail (i.e., within an angular separation of less than 4°) that become broadband in the far tail. The size of the interaction region at the equator is estimated to be 4.2 ± 0.9 Europa radii, consistent with previous estimates based on theory and UV observations. Plain Language Summary: The space environment close to Jupiter is dominated by the magnetic field of the giant planet in a so‐called magnetosphere. The four Galilean moons, including Europa, orbit deep inside the Jovian magnetosphere and therefore constantly interact with the rapidly rotating plasma flow made of charged particles trapped by the magnetic field of the giant planet. The interaction between moons and plasma generates electromagnetic waves, accelerate particles and produce emissions at various wavelengths, including bright UV auroral spots and tails in the atmosphere of Jupiter. In this work, we present 10 events where the Juno spacecraft observed both in situ and remotely the acceleration of electrons due to the interaction between the icy moon Europa and the magnetospheric environment. We characterize the properties of the accelerated electrons. In particular, we find that acceleration is maximum near the moon itself, and that two distinct families of electron distributions exist. Key Points: Juno unambiguously observed 10 events of downward electron acceleration from Europa at various downtail separations with the moonPrecipitating energy fluxes decrease exponentially as a function of downtail distance from the moon, with an e‐folding of 7.4°Two types of electron distributions exist: non‐monotonic in the near tail and broadband in the far tail
- Subjects
EUROPA (Satellite); ATMOSPHERE of Jupiter; JUNO (Space probe); PARTICLE emissions; PLASMA flow; ELECTRON distribution; LAGRANGIAN points
- Publication
Geophysical Research Letters, 2023, Vol 50, Issue 12, p1
- ISSN
0094-8276
- Publication type
Article
- DOI
10.1029/2023GL103131