An overviewof the radiation bursts observed by Juno-UVS above the polar regions

One of the surprising results from the Juno mission is the quasi-ubiquitous finding of anti-planetward charged particles escaping along the magnetic field lines from the polar-most regions. Some of these electrons are so energetic (on the order of 10MeV) that they can penetrate through Juno’s ultraviolet imaging spectrograph (Juno-UVS)’s shielding and hit the detector. Contrary to the continuous radiation bombardment that is typically observed when Juno crosses the radiation belt’s horns and which causes a quasi-continuous background on the UV images, the radiation-caused noise observed above the poles registers on the images as parallel stripes looking like bar-codes. In this study, we further explore these so-called bar-code events that have been observed during the 40 first Juno orbits and we essentially confirm earlier results based on a more limited number of observations. Among other results, we will show plots of their occurrence superposed to maps of the aurora, demonstrating that they are quasi-systematically connected to the polar region. We will also show that they mostly appear when UVS is pointed down to Jupiter, a signature of a field-aligned, up-going population. While there are upward MeV electron beams over a broader range of latitudes, the subset of the most intense beams is in the polar region. These beams are seen in the north and south but in the northern hemisphere they are more prevalent when the polar region is not illuminated.