Observations of Auroral "Raindrops" in Jupiter's Polar Region by Juno-UVS

Juno-UVS has observed Jupiter's FUV auroral emissions during multiple close flybys following Juno's orbital insertion on 5 July 2016. Each perijove provides a different snapshot of the Jovian auroral emissions recorded at different system III longitudes and local time conditions. We present the analysis of an auroral feature identified in Jupiter's polar region by Juno-UVS, characterized by faint (~100 kR) concentric circles of UV emission expanding with time. The features were found within Jupiter's polar auroral regions, i.e. inside of the main oval, both in the northern and southern hemispheres. These regions, connected to Jupiter's outer magnetosphere, are the most dynamic part of Jupiter's UV-aurora often exhibiting flares evolving over short timescales. As Juno spins at a rate of 2 rpm, UVS provides snapshots of regions smaller than the main auroral regions. Consecutive spins recorded over the same region allow identification and characterization of these auroral features. We characterize where the "raindrops"-like features occur within the auroral region and determine their expansion rates. We use the Vogt et al. (2011, 2015) magnetosphere-ionosphere mapping model coupled with the JRM09 magnetic field model to trace the origin of these emissions back to their origin in the magnetodisk. We discuss potential physical interpretations of such features.