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- Title
UVS Observations of Ganymede's Aurora During Juno Orbits 34 and 35.
- Authors
Greathouse, T. K.; Gladstone, G. R.; Molyneux, P. M.; Versteeg, M. H.; Hue, V.; Kammer, J. A.; Davis, M. W.; Bolton, S. J.; Giles, R. S.; Connerney, J. E. P.; Gerard, J.‐C.; Grodent, D. C.; Bonfond, B.; Saur, J.; Duling, S.
- Abstract
On 7 June 2021, Juno‐UVS mapped Ganymede's auroral emissions near a closest approach altitude of 1,046 km. The high spatial resolution map exhibits bright, 200–1,000 R, oxygen emissions organized into northern and southern auroral ovals. Though the map has incomplete global coverage, UVS observed longitudinal structure similar to that described by McGrath et al. (2013), https://doi.org/10.1002/jgra.50122 and latitudinal and vertical structure never before resolved. The mapped auroral emissions (a) display an intense narrow auroral curtain with a sharp poleward boundary, (b) have a more slowly decreasing equatorial edge on the leading hemisphere, (c) appear to originate near the surface with a vertical extent of 25–50 km, and (d) are slightly brighter in the north than the south. Additionally, we present UVS observations from the more distant Juno Ganymede flyby on 20 July 2021. We describe the observations, compare them to previous Hubble Space Telescope observations and current model predictions of the open‐closed‐field line‐boundary. Plain Language Summary: Observations of Ganymede by Juno‐UVS during a close flyby (during Juno's 34th Jupiter orbit) captured unique high‐spatial‐resolution measurements of Ganymede's auroral emissions. Organized into two polar ovals, the positions and intensities of the auroral emissions are consistent with previous Hubble Space Telescope observations. The observed morphology of the auroras on the leading hemisphere of Ganymede exhibits latitudinal structure never before resolved. Previous studies suggest the poleward edge of the emissions trace the poleward most position of the magnetic field lines that have both ends rooted to Ganymede. We show that a magnetic field model of Ganymede within Jupiter's larger magnetosphere predicts last‐closed field‐lines very close to the observed auroral emissions, as expected. More distant observations taken during Juno's following orbit (orbit 35) capture auroral emissions at slightly different longitudes. They too show similar agreement with previous observations and current magnetic field models. Key Points: The high spatial resolution observations revealed auroral emissions of over 1000 Rayleighs, brighter than previously observedThe leading hemisphere aurora exhibits an intense auroral curtain with a sharp poleward boundary and more slowly tapering equatorial edgeJuno‐UVS observed Ganymede's auroral emissions extending up to a maximum of 50 km altitude
- Subjects
ORBITS (Astronomy); AURORAS; SPACE telescopes; MAGNETIC fields; SPATIAL resolution
- Publication
Geophysical Research Letters, 2022, Vol 49, Issue 23, p1
- ISSN
0094-8276
- Publication type
Article
- DOI
10.1029/2022GL099794