C2H2 in Jupiter's atmosphere from Juno UVS observations: latitudinal distribution and localized enhancement within the auroral ovals
Abstract
The Ultraviolet Spectrograph (UVS) is a far-ultraviolet imaging spectrograph on NASA's Juno mission, which has been in a highly-elliptical polar orbit around Jupiter since July 2016. The primary scientific goal of UVS is to study Jupiter's auroral emissions and the instrument's spectral range of 68-210 nm was designed to cover several important H and H2 emission bands. However, the longer wavelengths covered by UVS extend into a spectral region that is dominated by reflected sunlight; this part of the spectrum is sensitive to hydrocarbons and aerosols in Jupiter's stratosphere, and C2H2 is the molecular species with the strongest spectral signature. We have combined reflected sunlight observations from the first 40 perijoves of the Juno mission in order to study the spatial distribution of C2H2 both latitudinally and within the polar regions. We find that the zonally-averaged C2H2 abundance decreases towards the poles by a factor of 2—4, but that within the auroral ovals there is a strong localized enhancement, a factor of 3 greater than the adjacent non-auroral regions. These ultraviolet observations provide an independent confirmation of results that have previously been obtained from infrared observations (Nixon et al., 2007, doi: 10.1016/j.icarus.2006.11.016, Sinclair et al., 2017, doi: 10.1016/j.icarus.2016.12.033). The latitudinal distribution is expected from insolation rates: near the equator, the UV solar flux is higher, allowing more C2H2 to be generated from the UV photolysis of CH4. The decrease in abundance towards the poles suggests that horizontal mixing rates are not rapid enough to homogenize the latitudinal distribution. The localized enhancement within the auroral oval is likely driven by auroral processes; the influx of charged particles leads to an increase in ion-neutral and electron recombination reactions which favor the production of C2H2.
- Publication:
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AGU Fall Meeting Abstracts
- Pub Date:
- December 2022
- Bibcode:
- 2022AGUFM.P32C1850G