Satellite Footprints Seen in Jupiter Aurora

Where are the footprints of Jupiter's moons, and what causes them?

Each footprint is represented by a bright dot. Io's footprint is at far left; Ganymede's is just below and to the right of center; and Europa's is to the right of Ganymede's signature. These emissions, produced by electric currents generated by the moons, flow along Jupiter's magnetic field, bouncing in and out of the upper atmosphere. They are unlike anything seen on Earth.