Abstract
Auroral brightness and color ratio imagery, captured using the Juno
mission’s Ultraviolet Spectrograph, display intense emissions poleward
of Jupiter’s northern main emission, and these are split into two
distinctly different spectral or “color ratio” regimes. The most
poleward region, designated the “swirl region” by Grodent et al.
(2003), exhibits a high color ratio, while low color ratio emissions are
found within the collar around the swirl region but still poleward of
the main emission. We confirm the apparent strong magnetospheric local
time control within the polar collar (Grodent et al., 2003), with the
dusk side bright “active region” emissions extending from
~11 to 22 hr of magnetospheric local time. These bright
emissions dim by at least an order of magnitude between
~0 and 11 hr magnetospheric local time, in the midnight
to dawn side “dark region”. This magnetospheric local time structure
holds true even when the entire northern oval is located on the night
side of the planet (in ionospheric local time), a geometry unstudied
prior to Juno, as it is unobservable from Earth. The swirl region
brightens at ionospheric dawn (~5-7 ionospheric local
time) and diminishes or completely disappears at ionospheric local times
of ~20 to 22 hrs. Finally, the southern auroral polar
emissions appear to share all of the local time dependencies of its
northern counterpart, but at a reduced intensity.