North and South: Simultaneous observations of both Jovian poles from Juno and the Hubble Space Telescope

On its elongated orbit, Juno flies over the poles of Jupiter every 53.5 days. The few hours
before and after the perijove offer unique opportunities to observe the whole polar region
from close distance. However, Juno’s instruments can only observe one hemisphere at a time.
Fortunately, the Hubble Space Telescope points its 2.4 m mirror toward the opposite
hemisphere during some of these time intervals, providing truly simultaneous observations of
both poles. We compare observations from Juno-UVS with Far-UV imaging sequences from
the Hubble’s Space Telescope Imaging Spectrograph (STIS). Juno-UVS acquires spectrally
resolved images of 17 ms exposure every 30 s Juno spin in the 70-205 nm wavelength range,
while STIS can acquire about 270 consecutive 10 s images per HST orbit in the 130-160 nm
range, but without any spectral resolution. Despite some differences, these datasets are
similar enough in terms of spectral coverage, temporal and spatial resolution to allow direct
comparisons. On Jupiter, the magnetic field is highly asymmetric and displays significant
localized anomalies. Furthermore, most processes leading to auroral emissions depend on the
magnetic field magnitude, either in the equatorial plane, in the acceleration regions, or in the
upper atmosphere. Investigating morphological and brightness discrepancies between the two
hemispheres provides precious clues on the current systems flowing in the magnetosphere
and on the charged particles acceleration mechanisms.