A Juno‐Era View of Electric Currents in Jupiter's Magnetodisk

Abstract

AbstractRecent 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 (FACs) 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 about 25 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 ∼1,500 kg/s.