Variability of Jupiter's Main Auroral Emission and Satellite Footprints Observed With HST During the Galileo Era. Issue 2 (27th January 2022)

• Record Type: Journal Article
• Authors: Vogt, Marissa F.; Rutala, Matthew; Bonfond, Bertrand; Clarke, John T.; Moore, Luke; Nichols, Jonathan D.
• Is Part Of: Journal of geophysical research. Volume 127:Issue 2(2022)
• Page Start: n/a
• Page End: n/a
• Publication Date: 2022-01-27
• Subjects: Jupiter -- planetary magnetospheres -- planetary aurora; Magnetospheric physics -- Periodicals; Space environment -- Periodicals; Cosmic physics -- Periodicals; Planets -- Atmospheres -- Periodicals; Heliosphere (Astrophysics) -- Periodicals; Geophysics -- Periodicals; 523.01
• DOI: 10.1029/2021JA030011
• Languages: English
• ISSNs: 2169-9380

Abstract

Abstract: Hubble Space Telescope images of Jupiter's UV aurora show that the main emission occasionally contracts or expands, shifting toward or away from the magnetic pole by several degrees in response to changes in the solar wind dynamic pressure and Io's volcanic activity. When the auroral footprints of the Galilean satellites move with the main emission this indicates a change in the stretched field line configuration that shifts the ionospheric mapping of a given radial distance at the equator. However, in some cases, the main emission shifts independently from the satellite footprints, indicating that the variability stems from some other part of the corotation enforcement current system that produces Jupiter's main auroral emissions. Here, we analyze HST images from the Galileo era (1996–2003) and compare latitudinal shifts of the Ganymede footprint and the main auroral emission. We focus on images with overlapping Galileo measurements because concurrent measurements are available of the current sheet strength, which indicates the amount of field line stretching and can influence both the main emission and satellite footprints. We show that the Ganymede footprint and main auroral emission typically, but do not always, move together. Additionally, we find that the auroral shifts are only weakly linked to changes in the current sheet strength measured by Galileo. We discuss implications of the observed auroral shifts in terms of the magnetospheric mapping. Finally, we establish how the statistical reference main emission contours vary with central meridian longitude and show that the dependence results from magnetospheric local time asymmetries. Plain Language Summary: Jupiter's main auroral emission is thought to be the result of a current system that develops to help circulate plasma from Io as it moves through Jupiter's magnetosphere. There are many factors that can influence the position and brightness of Jupiter's main emission, including the solar wind and internal factors like Io's volcanic activity. The auroral footprints of Jupiter's moons Io, Europa, and Ganymede can provide important clues to what factors influence variability in the main auroral emission because some processes, like those that affect the radial stretching of the magnetic field, will affect the position of both the satellite footprints and the main emission. In this study, we quantify and compare variability in the position of Jupiter's main auroral emission and the Ganymede footprint in images from the Hubble Space Telescope. We focus on images from the Galileo era (1996–2003) and compare variability in the auroral emissions to Galileo observations of magnetospheric variability. We find that the Ganymede footprint and main auroral emission typically change in the same way, but find the expected relationship between the auroral motion and the magnetic field measured by Galileo to be weak. Key Points: We compared Jupiter's auroral variability from HST images to concurrent measurements of magnetospheric activity from the Galileo spacecraft We found that the Ganymede footprint and main emission show similar variability but are not strongly linked to magnetospheric conditions The position of the main emission depends on central meridian longitude, which reflects the importance of magnetospheric local time asymmetries