UV-Dark Polar Ovals on Jupiter Trace the Depth of Magnetosphere-Atmosphere Connection

Abstract

We observe twenty-six global maps of Jupiter between 1994 and 2022 taken with HST WFPC2/F255W and WFC3/F275W, detecting transient UV dark ovals in the southern polar hood haze layer with a 48–53% frequency of occurrence. We find that the dark oval is an anticyclonic vortex that remains within the main southern auroral oval during most of its lifetime; these behaviors match previous observations of a similar dark oval near the north pole. The southern dark oval appears 4–6 times more frequently than its northern counterpart. Using a radiative transfer model, we find that these auroral effects cause a 20–50 times increase in haze abundance in the dark oval region and/or an overall upward shift in the stratospheric haze distribution. We estimate that the anticyclonic vorticity of the dark oval is enhanced relative to the surroundings, representing a deep continuation of higher-altitude vortices previously observed in the thermosphere and upper stratosphere. The feature is likely driven by magnetospheric momentum exchange, with enhanced aerosols producing the localized heating detected in prior infrared retrievals.