Abstract
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.