First Estimate of Wind Fields in the Jupiter Polar Regions From JIRAM-Juno Images

We present wind speeds at the similar to 1bar level at both Jovian polar regions inferred from the 5-m infrared images acquired by the Jupiter InfraRed Auroral Mapper (JIRAM) instrument on the National Aeronautics and Space Administration Juno spacecraft during its fourth periapsis (2 February 2017). We adopted the criterion of minimum mean absolute distortion (Gonzalez & Woods, 2008) to quantify the motion of cloud features between pairs of images. The associated random error on speed estimates is 12m/s in the northern polar region and 9.8m/s at the south. Assuming that polar cyclones described by Adriani et al. (2018, ) are in rigid motion with respect to System III, tangential speeds in the interior of the vortices increase linearly with distance from the center. The annulus of maximum speed for the main circumpolar cyclones is located at approximatively 1,000km from their centers, with peak cyclonic speeds typically between 80 and 110m/s and similar to 50m/s in at least two cases. Beyond the annulus of maximum speed, tangential speed decreases inversely with the distance from the center within the Southern Polar Cyclone and somewhat faster within the Northern Polar Cyclone. A few small areas of anticyclonic motions are also identified within both polar regions.