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Source of radio emissions induced by the Galilean moons Io, Europa and Ganymede: in situ measurements by Juno
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Source of radio emissions induced by the Galilean moons Io, Europa and Ganymede: in situ measurements by Juno

C. K Louis, P Louarn, B Collet, N Clément, S. Al Saati, J. R Szalay, V Hue, L Lamy, S Kotsiaros, W. S Kurth, …
ArXiv.org
Cornell University
08/10/2023
DOI: 10.48550/arxiv.2308.05541
url
https://doi.org/10.1029/2023JA031985View
Published (Version of record)This article has now been published in a journal and has been peer-reviewed by subject experts. This version may differ significantly from the preprint version. Access restricted to faculty, staff and students
url
https://doi.org/10.48550/arXiv.2308.05541View
Preprint (Author's original)This preprint has not been evaluated by subject experts through peer review. Preprints may undergo extensive changes and/or become peer-reviewed journal articles. Open Access

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Abstract

At Jupiter, part of the auroral radio emissions are induced by the Galilean moons Io, Europa and Ganymede. Until now, except for Ganymede, they have been only remotely detected, using ground-based radio-telescopes or electric antennas aboard spacecraft. The polar trajectory of the Juno orbiter allows the spacecraft to cross the range of magnetic flux tubes which sustain the various Jupiter-satellite interactions, and in turn to sample in situ the associated radio emission regions. In this study, we focus on the detection and the characterization of radio sources associated with Io, Europa and Ganymede. Using electric wave measurements or radio observations (Juno/Waves), in situ electron measurements (Juno/JADE-E), and magnetic field measurements (Juno/MAG) we demonstrate that the Cyclotron Maser Instability (CMI) driven by a loss-cone electron distribution function is responsible for the encountered radio sources. We confirmed that radio emissions are associated with Main (MAW) or Reflected Alfv\'en Wing (RAW), but also show that for Europa and Ganymede, induced radio emissions are associated with Transhemispheric Electron Beam (TEB). For each traversed radio source, we determine the latitudinal extension, the CMI-resonant electron energy, and the bandwidth of the emission. We show that the presence of Alfv\'en perturbations and downward field aligned currents are necessary for the radio emissions to be amplified.

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