Variability and Hemispheric Symmetry of the Pedersen Conductance in the Jovian Aurora

摘要

Ionospheric conductance contributes to regulate the characteristics of the ionospheric current and the closure of the magnetosphere-ionosphere circuit in the ionosphere. Measurements of Birkeland currents with the Juno magnetometer have indicated that they are statistically larger in the south. It has been suggested that these asymmetries may be the consequence of a higher Pedersen conductance in the southern hemisphere. We have derived the local precipitated electron energy flux and their characteristic energy from 14 multi-spectral images collected with the ultraviolet spectrograph on board Juno. This information was then used as input to an ionospheric model providing the density of H_3~+, H+, and hydrocarbon ions to calculate the spatial distribution of the Pedersen conductance for Juno perijoves 1-15. We show that the area-integrated conductance is closely proportional to the H_3~+ ion content and quasi equal in the north and the south. The mean conductance is 0.47 mho in both hemispheres. However, local variations in the Pedersen conductivity and/or hemispheric differences between the magnetospheric rotation and the rotation velocities of the neutrals can also result in asymmetry of Birkeland currents.