An Overview of Juno-UVS Observations of Jupiter’s Auroras through Perijove 6

Currently, Juno’s Ultraviolet Spectrograph (UVS) has observed the Jovian aurora during
five perijove passes. On each pass, UVS observes Jupiter for 10 hours centered on closest
approach in a series of swaths, with one swath per 30s spin of the Juno spacecraft. During
this time the range to the aurora drops from 6 RJ to 0.3 RJ or less in the north (and
reverses this in the south), so that spatial resolution and coverage change dramatically. The
UVS scan mirror is used to target di
ff
erent features, as the auroral regions are generally
much larger than UVS’s 7-degree long slit can accommodate in a single swath. Typically,
the scan mirror position is changed every 2 -5 Juno spins, to track specific targets or just
raster across the entire auroral region. Since UVS only observes any particular location for
17 ms/swath, the series of swaths provide snapshots of ultraviolet auroral brightness and
color. A variety of forms and activity levels are represented in this data set, and many have
been described before with HST observations, but are seen here with higher spatial
resolution. One interesting result is that in false color images (where RGB colors are
assigned to long, medium, and short UV wavelengths, respectively), the emission morphology
often alternates red and blue, in a way similar to patterns expected of large scale current
systems. Further results which emerge as the UVS data are compared with data from the
other Juno auroral instruments will also be presented.