UV-Dark Polar Ovals on Jupiter as Tracers of Magnetosphere-Atmosphere Connection

Aerosols in Jupiter’s stratosphere form intriguing polar hoods, which have been investigated by ultraviolet cameras on Cassini and the Hubble Space Telescope. Transient, concentrated dark ovals of unknown origin have been noted within both the northern and southern polar hoods. Here, we use twenty-six global maps of Jupiter taken by Hubble between1994 and 2022, detecting transient UV-dark ovals with a 48 to 53%frequency of occurrence in the south. We find the southern dark oval to be 4 to 6 times more common than its northern counterpart. The southern feature is an anticyclonic vortex, remaining within the auroral oval during most of its lifetime. The oval’s darkness is consistent with a 20 to 50 times increase in haze abundance and/or an overall upward shift in the stratospheric haze distribution. The anticyclonic vorticity of the dark oval is enhanced relative to its surroundings, representing a deep extension of higher-altitude vortices previously reported in the thermosphere and upper stratosphere. The haze enhancement is likely driven by magnetospheric momentum exchange, with enhanced aerosols producing the localized heating detected in prior infrared retrievals.