Morphology of Jupiter's Polar Auroral Bright Spot Emissions via Juno‐UVS Observations

Since 2016, the Juno‐UVS (Ultraviolet Spectrograph) instrument has been taking spectral images of Jupiter's auroras in their full extent, including the nightside, which cannot be viewed from Earth. We present a systematic analysis of features in Jupiter's polar auroras called auroral bright spots, which were observed by Juno‐UVS during the first 25 orbits of the spacecraft. An auroral bright spot is an isolated localized and transient brightening in the polar region. Bright spots were identified in 16 perijoves (PJ) out of 24, mostly in either the northern or the southern hemisphere but rarely in both during the same PJ. 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 PJs, bright spots exhibit quasiperiodic behavior. The spots, within PJ4 and PJ16, each reappeared within <2,000 km from the previous position in System III with periods of 28 and 22 min, respectively. This period is similar to periods previously identified in X‐rays and various other observations. The bright spot positions are 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, the bright spots can be seen at any local time, rather than being confined to the noon sector as previously thought from Earth‐based observations. This suggests that the bright spots might not be firmly connected to the noon facing magnetospheric cusp processes. During the first 25 perijoves of the Juno mission, the Ultraviolet Spectrograph instrument observed transient bright spots at the edge of the swirl regionDuring longer continuous observing sequences, the bright spots reoccurred at approximately the same System III location every ∼25 minThe bright spots were not fixed at noon or any other local time, which excludes any explanations involving an Earth‐like noon‐facing cusp During the first 25 perijoves of the Juno mission, the Ultraviolet Spectrograph instrument observed transient bright spots at the edge of the swirl region During longer continuous observing sequences, the bright spots reoccurred at approximately the same System III location every ∼25 min The bright spots were not fixed at noon or any other local time, which excludes any explanations involving an Earth‐like noon‐facing cusp