Comparing Electron Energetics and UV Brightness in Jupiter's Northern Polar Region During Juno Perijove 5. Issue 1 (8th January 2019)

• Record Type: Journal Article
• Authors: Ebert, R. W.; Greathouse, T. K.; Clark, G.; Allegrini, F.; Bagenal, F.; Bolton, S. J.; Connerney, J. E. P.; Gladstone, G. R.; Imai, M.; Hue, V.; Kurth, W. S.; Levin, S.; Louarn, P.; Mauk, B. H.; McComas, D. J.; Paranicas, C.; Szalay, J. R.; Thomsen, M. F.; Valek, P. W.; Wilson, R. J.
• Is Part Of: Geophysical research letters. Volume 46:Issue 1(2019)
• Page Start: 19
• Page End: 27
• Publication Date: 2019-01-08
• Subjects: Juno -- Jupiter's aurora -- polar auroral region -- polar UV emissions -- precipitating electrons -- electron energy flux; Geophysics -- Periodicals; Planets -- Periodicals; Lunar geology -- Periodicals; 550
• DOI: 10.1029/2018GL081129
• Languages: English
• ISSNs: 0094-8276

Abstract

Abstract: We compare electron and UV observations mapping to the same location in Jupiter's northern polar region, poleward of the main aurora, during Juno perijove 5. Simultaneous peaks in UV brightness and electron energy flux are identified when observations map to the same location at the same time. The downward energy flux during these simultaneous observations was not sufficient to generate the observed UV brightness; the upward energy flux was. We propose that the primary acceleration region is below Juno's altitude, from which the more intense upward electrons originate. For the complete interval, the UV brightness peaked at ~240 kilorayleigh (kR); the downward and upward energy fluxes peaked at 60 and 700 mW/m 2, respectively. Increased downward energy fluxes are associated with increased contributions from tens of keV electrons. These observations provide evidence that bidirectional electron beams with broad energy distributions can produce tens to hundreds of kilorayleigh polar UV emissions. Plain Language Summary: Jupiter's ultraviolet (UV) aurora is produced by electrons that precipitate into the planet's atmosphere and interact with hydrogen molecules. A number of different UV auroral emission regions have been identified such as the main aurora, the aurora associated with Jupiter's satellites, and the polar aurora located poleward of the main aurora. We examine electron and UV observations from Juno in Jupiter's northern polar region to investigate the processes responsible for producing Jupiter's polar aurora. We show electrons and UV emissions having simultaneous enhancements during a time when they map to the same location of Jupiter's upper atmosphere at the same time. We present evidence that electrons with energies between 0.1 and 100 kilo electron volts (keV) are capable of producing the polar UV emissions studied here and that further acceleration of these electrons may be occurring at altitudes below the spacecraft. Key Points: Simultaneous peaks are observed in electron energy flux and UV brightness when they map to same location in Jupiter's polar region at the same time Upward greater than downward electron energy fluxes are observed, suggesting that primary acceleration region may be below ~1.5 jovian radii Downward energy fluxes able to produce tens to hundreds of kilorayleigh polar UV emissions are identified; increases in energy flux due to tens of keV electrons