Variability and Hemispheric Symmetry of the Pedersen Conductance in the Jovian Aurora. Issue 4 (30th March 2021)

• Record Type: Journal Article
• Authors: Gérard, J.‐C.; Gkouvelis, L.; Bonfond, B.; Grodent, D.; Gladstone, G. R.; Hue, V.; Greathouse, T. K.; Kammer, J. A.; Versteeg, M.; Giles, R. S.
• Is Part Of: Journal of geophysical research. Volume 126:Issue 4(2021)
• Page Start: n/a
• Page End: n/a
• Publication Date: 2021-03-30
• Subjects: aurora -- conductivity -- ionosphere -- Juno -- Jupiter -- ultraviolet; Magnetospheric physics -- Periodicals; Space environment -- Periodicals; Cosmic physics -- Periodicals; Planets -- Atmospheres -- Periodicals; Heliosphere (Astrophysics) -- Periodicals; Geophysics -- Periodicals; 523.01
• DOI: 10.1029/2020JA028949
• Languages: English
• ISSNs: 2169-9380

Abstract

Abstract: 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 H3 +, 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 H3 + 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 t he rotation velocities of the neutrals can also result in asymmetry of Birkeland currents. Plain Language Summary: The electric conductance of Jupiter's partly controls the currents that circulate in its ionosphere and the current loops closing in this conducting region. Measurements of the ionospheric current intensity with the magnetometer along Juno's trajectory have shown that these currents are statistically stronger in the southern than in the northern hemisphere. A possibility has been raised that this asymmetry is related to a higher value of the Pedersen conductivity in the south. To test this hypothesis, we have compared the vertically integrated conductivity in both hemispheres derived from the intensity and spectral composition of images obtained with the Juno Ultraviolet Spectral Imager during its first 15 orbits around Jupiter. Comparison of the pairs of global conductance maps indicates that there is no significant statistical conductance asymmetry as both the area‐integrated and the mean conductivity are quasi equal in the two hemispheres. Possible causes for the observed ionospheric current asymmetries are the local aspect of the magnetometer measurements and/or hemispheric differences between the magnetospheric rotation and the rotation velocities of the neutrals. Key Points: We have built and compared 28 Pedersen conductance maps based on ultraviolet spectrograph spectral images collected during the 15 first Juno orbits The mean conductance is 0.47 mho in both hemispheres, a symmetry in contrast with the asymmetry observed in the ionospheric currents The auroral H2 emitted power varies between 1.1 and 3.6 TW but the north/south power ratio is close to unity on the average