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 Alfvén 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 Alfvén perturbations and downward field aligned currents are necessary for the radio emissions to be amplified.

Recent observations from Juno provided a detailed view of Jupiter’s magnetodisk, including its magnetic fields, waves, plasmas and energetic particles. Here, we contribute to Juno results by determining the electric currents threading the magnetodisk and their coupling to field-aligned currents (FAC) in the midnight-to-dawn local time sector. We first derive from Juno magnetic field data the spatial distributions of the height-integrated radial (Ir) and azimuthal (Ia) currents in the magnetodisk, and then calculate the FACs from the divergence of the two current components. The Ir-associated FAC, Jr, flows into and out of the magnetodisk at small and large radial distances, respectively, approximately consistent with the axisymmetric corotation enforcement model. On the other hand, Ia decreases with increasing local time everywhere in the local time sector covered, indicating an additional FAC (Ja) flowing out of the magnetodisk. From Ia and Ja, we conclude that the influence of the solar wind, which compresses the dayside magnetosphere and thus breaks the axisymmetry of currents and fields, reaches deep to a radial distance of at least 20 Jupiter radii. Our results provide observational constraints on Jupiter’s magnetosphere-ionosphere-thermosphere coupling current systems, on their relation to the main auroral emission and on the radial mass transport rate in the magnetodisk, which we estimate to be close to ~1500 kg/s.