Spatial Distribution of the Pedersen Conductance in the Jovian Aurora From Juno‐UVS Spectral Images. Issue 8 (19th August 2020)

• Record Type: Journal Article
• Authors: Gérard, J.‐C.; Gkouvelis, L.; Bonfond, B.; Grodent, D.; Gladstone, G. R.; Hue, V.; Greathouse, T. K.; Versteeg, M.; Kammer, J. A.; Blanc, M.
• Is Part Of: Journal of geophysical research. Volume 125:Issue 8(2020)
• Page Start: n/a
• Page End: n/a
• Publication Date: 2020-08-19
• Subjects: Jupiter -- aurora -- conductivity -- ionospheric current -- Juno -- ultraviolet; Magnetospheric physics -- Periodicals; Space environment -- Periodicals; Cosmic physics -- Periodicals; Planets -- Atmospheres -- Periodicals; Heliosphere (Astrophysics) -- Periodicals; Geophysics -- Periodicals; 523.01
• DOI: 10.1029/2020JA028142
• Languages: English
• ISSNs: 2169-9380

Abstract

Abstract: Ionospheric conductivity perpendicular to the magnetic field plays a crucial role in the electrical coupling between planetary magnetospheres and ionospheres. At Jupiter, it controls the flow of ionospheric current from above and the closure of the magnetosphere‐ionosphere circuit in the ionosphere. We use multispectral images collected with the Ultraviolet Spectral (UVS) imager on board Juno to estimate the two‐dimensional distribution of the electron energy flux and characteristic energy. These values are fed to an ionospheric model describing the generation and loss of different ion species, to calculate the auroral Pedersen conductivity. The vertical distributions of H3 +, hydrocarbon ions, and electrons are calculated at steady state for each UVS pixel to characterize the spatial distribution of electrical conductance in the auroral region. We find that the main contribution to the Pedersen conductance stems from collisions of H3 + and heavier ions with H2 . However, hydrocarbon ions contribute as much as 50% to Σp when the auroral electrons penetrate below the homopause. The largest values are usually associated with the bright main emission, the Io auroral footprint and occasional bright emissions at high latitude. We present examples of maps for both hemispheres based on Juno‐UVS images, with Pedersen conductance ranging from less than 0.1 to a few mhos. Plain Language Summary: One of the quantities characterizing the ability of ionospheres to carry currents perpendicular to the magnetic field is the altitude integrated Pedersen conductivity. On Jupiter, it is an important quantity that partly controls how electric currents can flow between the magnetosphere and the high‐latitude ionosphere. It is therefore a key element in the understanding of how and where the Jovian aurora is formed and an important input to numerical models of auroral precipitation. We use observations from the UltraViolet spectral imager near Juno's closest approach to Jupiter to remotely characterize the flux of energy carried by the auroral electrons and their mean energy. These quantities are evaluated for each instrumental pixel and used as inputs to a model to map the Pedersen integrated conductivity. The main contributions to the conductance are caused by collisions between H3 + and hydrocarbon ions such as CH5 + and C3 Hn + with neutral constituents. We present examples of Pedersen conductance maps for both hemispheres. We find that the conductance is spatially very variable with values ranging from less than 0.1 to several mhos. The largest values are usually associated with the bright main emission, the Io auroral footprint and occasional bright emissions at high latitude. Key Points: Multispectral auroral observations from UVS‐Juno are used to map the auroral ionospheric Pedersen conductance in both hemispheres H3 + and hydrocarbon ions make most of the contribution to auroral ionospheric conductance The conductance varies from less than 0.1 up to several mhos in the main aurora, high latitude precipitation, and Io magnetic footprint