Satellite-magnetosphere interactions at Jupiter: A review of Juno JADE/JEDI observations

Abstract: 

Due to its inclined and highly elliptical trajectory, the Juno spacecraft passed frequently through magnetic flux tubes that were connected to the orbits of the Galilean satellites-Io, Europa, Ganymede, and Callisto. Meanwhile, due to its orbital precession, Juno has also sampled the equatorial regions of the magnetosphere in the vicinity of the moons. This has provided for timely opportunities for Juno to study both the far-field as well as the near interaction of the moons with the magnetosphere. In this seminar, I will review the in-situ plasma observations made by Juno spacecraft’s JADE and JEDI instruments in both regions. 

Juno has made some intriguing observations in the equatorial regions, e.g., protons accelerated within the Io flux tube, H2+ pickup-ions likely from Europa, and observations made during the close Ganymede flyby in 2021. Mission-averaged pitch angle distributions of protons in the equatorial region show that energetic protons are mostly field-aligned, which I will argue could be a result of adiabatic transport of protons which originate from Jupiter, or of charge exchange with a neutral torus present between Europa and Ganymede. 

I will also discuss the plasma observations during satellite flux tube crossings in the polar regions. In the Io and Europa flux tubes, Juno has observed broadband electron fluxes, broadband proton fluxes, and intense wave activity. The energy flux of the electrons and the Poynting flux is well correlated and decreases the further the crossing is in the moon’s wake. Lastly, I will show some new observations of proton and electron distributions within the Io, Europa, and Ganymede wake flux tubes, that exhibit flux enhancements at discrete energies, likely due to bounce-resonant acceleration with the standing Alfvén wave system generated by the satellite-magnetosphere interaction.