Morphology of Jupiter's Polar Auroral Bright Spot Emissions via Juno-UVS
Observations
Abstract
Since 2016, the Juno-UVS instrument has been taking spectral images of
Jupiter’s auroras during its polar fly-bys. These observations provide a
great opportunity to study Jupiter’s auroras in their full extent,
including the nightside, which is inaccessible from Earth. We present a
systematic analysis of features in Jupiter’s polar auroras called
auroral bright spots observed during the first 25 Juno orbits. Bright
spots were identified in 16 perijoves (PJ) out of 24 (there was no
available data for perijove 2), in both the northern and southern
hemispheres. The emitted power of the bright spots is time variable with
peak power ranging from a few tens to a hundred of gigawatts. Moreover,
we found that, for some perijoves, bright spots exhibit quasiperiodic
behavior. The spots, within PJ4 and PJ16, each reappeared at almost the
same system III position of their first appearance with periods of 28
and 22 minutes, respectively. This period is similar to that of
quasiperiodic emissions previously identified in X-rays and various
other observations. The bright spot position is in a specific region in
the northern hemisphere in system III, but are scattered around the
magnetic pole in the southern hemisphere, near the edge of the swirl
region. Furthermore, our analysis shows that the bright spots can be
seen at any local time, rather than being confined to the noon sector as
previously thought based on biased observations. This suggests that the
bright spots might not be firmly connected to the noon facing
magnetospheric cusp processes.