Juno observations of spot structures and a split tail in Io-induced aurorae on Jupiter

Jupiter’s aurorae are produced in its upper atmosphere when incoming high-energy electrons precipitatealong the planet’s magnetic field lines. A northern and a southern main auroral oval are visible, surrounded by small emission features associated with the Galilean moons. We present infrared observations, obtained with the Juno spacecraft, showing that in the case of Io, this emission exhibits a swirling pattern that is similar in appearance to a von Karman vortex street. Well downstream of the main auroral spots, the extended tail is split in two. Both of Ganymede’s footprints also appear as a pair of emission features, which may provide a remote measure of Ganymede’s magnetosphere. These features suggest that the magnetohydrodynamicinteraction between Jupiterand its moon is more complex than previously anticipated.