Enhanced C$_2$H$_2$ absorption within Jupiter's southern auroral oval from Juno UVS observations

TL;DR

This study uses Juno UVS data to reveal that acetylene absorption is significantly enhanced within Jupiter's southern auroral oval, indicating auroral particle influence on upper-atmosphere chemistry.

Contribution

It provides the first evidence of localized C2H2 abundance enhancement in Jupiter's southern auroral region using UV reflectance data.

Findings

C2H2 absorption varies across the polar region.

Enhanced C2H2 abundance coincides with the southern aurora.

Poleward of the auroral oval, C2H2 is three times more abundant.

Abstract

Reflected sunlight observations from the Ultraviolet Spectrograph (UVS) on the Juno spacecraft were used to study the distribution of acetylene (C$_2$H$_2$) at Jupiter's south pole. We find that the shape of the C$_2$H$_2$ absorption feature varies significantly across the polar region, and this can be used to infer spatial variability in the C$_2$H$_2$ abundance. There is a localized region of enhanced C$_2$H$_2$ absorption which coincides with the location of Jupiter's southern polar aurora; the C$_2$H$_2$ abundance poleward of the auroral oval is a factor of 3 higher than adjacent quiescent, non-auroral longitudes. This builds on previous infrared studies which found enhanced C$_2$H$_2$ abundances within the northern auroral oval. This suggests that Jupiter's upper-atmosphere chemistry is being strongly influenced by the influx of charged auroral particles and demonstrates the necessity of developing ion-neutral photochemical models of Jupiter's polar regions.