Jovian auroral conductance from Juno-UVS: hemispheric asymmetry?

Ionospheric conductance is important in controlling the electrical coupling between the Jovian planetary magnetosphere and its ionosphere. To some extent, it regulates the characteristics of the ionospheric current from above and the closure of the magnetosphere-ionosphere circuit in the ionosphere (Cowley&Bunce, 2001). Multi-spectral images collected with the UltraViolet Spectrograph (UVS) (Gladstone et al., 2017) on board Juno (Bagenal et al.,2017) have been analyzed to derive the spatial distribution of the auroral precipitation reaching the atmosphere (Bonfond et al., 2017). Electron energy flux and their characteristic energy have been used as inputs to an ionospheric model providing the production and loss rates of the main ion species, H₃⁺, hydrocarbon ions and electrons (Gérard et al., 2020). Their steady state densities are calculated and used to determine the local distribution of the Pedersen electrical conductivity and its altitude integrated value for each UVS pixel. These values are displayed as H₃⁺ density and Pedersen conductivity maps. We find that the main contribution to the Pedersen conductance corresponds to collisions of H₃⁺ and hydrocarbon ions with H₂.

Analysis of the Birkeland current intensities based on the Juno magnetometers measurements (Kotsiaros et al. 2019) indicated that the observed current intensities are statistically larger in the south. They suggested that these differences are possibly due to a higher Pedersen conductance in this hemisphere. In order to verify this hypothesis, we calculate the conductance and H₃⁺ density maps for perijoves 1 to 15 based on Juno-UVS spectral images. We compare the spatially integrated auroral conductance values of the two hemispheres for each orbit.  The objective is to identify possible hemispheric asymmetries.   

REFERENCES

Bagenal, F., et al. (2017). Magnetospheric science objectives of the Juno mission. Space Science Reviews, 213(1-4), 219-287.

Bonfond, B., et al. (2017). Morphology of the UV aurorae Jupiter during Juno's first perijove observations. Geophysical Research Letters, 44(10), 4463-4471.

Cowley, S.W.H. & Bunce, E.J. (2001). Origin of the main auroral oval in Jupiter’s coupled magnetosphere–ionosphere system. Planet. Space Sci. 49, 1067–1088.

Gérard et al., Spatial distribution of the Pedersen conductance in the Jovian aurora from Juno-UVS spectral images, J. Geophys. Res., in press.

Gladstone et al. (2017). The ultraviolet spectrograph on NASA’s Juno mission. Space Science Reviews, 213(1-4), 447-473.

Kotsiaros, S. et al. (2019). Birkeland currents in Jupiter’s magnetosphere observed by the polar-orbiting Juno spacecraft. Nature Astronomy, 3(10), 904-909.