Evidence for Auroral Emissions From Callisto's Footprint in HST UV Images. Issue 1 (15th January 2018)

• Record Type: Journal Article
• Authors: Bhattacharyya, Dolon; Clarke, John T.; Montgomery, Jordan; Bonfond, Bertrand; Gérard, Jean‐Claude; Grodent, Denis
• Is Part Of: Journal of geophysical research. Volume 123:Issue 1(2018)
• Page Start: 364
• Page End: 373
• Publication Date: 2018-01-15
• Subjects: Jupiter -- aurora -- Callisto -- ultraviolet -- HST; Magnetospheric physics -- Periodicals; Space environment -- Periodicals; Cosmic physics -- Periodicals; Planets -- Atmospheres -- Periodicals; Heliosphere (Astrophysics) -- Periodicals; Geophysics -- Periodicals; 523.01
• DOI: 10.1002/2017JA024791
• Languages: English
• ISSNs: 2169-9380

Abstract

Abstract: Auroral emissions are expected from the footprint of Callisto in Jupiter's upper atmosphere owing to the known interaction of its atmosphere with Jupiter's magnetosphere, and from the observed auroral emissions from the footprints of the other three Galilean satellites. The mapping of Callisto along modeled magnetic field lines at Jupiter, however, places the expected footprint at the same latitude as the main auroral emissions, making it difficult to detect. We analyzed ultraviolet images of Jupiter taken using the Hubble Space Telescope/Advanced Camera for Surveys instrument during a large observing campaign in 2007. Using a coaddition method similar to one used for Enceladus, we have identified a strong candidate for the footprint of Callisto on 24 May 2007. We tested this finding by applying the same coaddition technique to a nearly identical auroral configuration on 30 May 2007 when Callisto was behind Jupiter, not visible from Earth (central meridian longitude = 22°; sub‐Callisto system III longitude = 327°). By comparing the two coadded images, we can clearly see the presence of a strongly subcorotating spot close to the expected Callisto footprint location on 24 May and its absence on 30 May. On 24 May Callisto was located in the current sheet. We also found a probable candidate on 26 May 2007 during which time Callisto was positioned below the current sheet. The measured location and intensity of the auroral emission provide important information about the interaction of Callisto with Jupiter's magnetic field, the corotating plasma, and the neutral and ionized state of the thin atmosphere of Callisto. Key Points: UV emissions from Callisto's auroral footprint detected using HST observations Jupiter's main auroral emission was dim and shifted equatorward for the candidate detections Callisto's auroral footprint emitted power is similar to that of Ganymede