Dawn-dusk asymmetry in the main auroral emissions at Jupiter observed with Juno-UVS

Abstract

Jupiter's main auroral emissions usually form auroral curtains surrounding the magnetic poles. Most explanations for this auroral feature are based on corotation enforcement currents flowing between the magnetosphere and the ionosphere. This process predicts the highest emitted power to originate from the dawn region, while the lowest emitted power would come from the noon to dusk region. However, a previous study using Hubble Space Telescope data showed the opposite, with a higher emitted power in the dusk region in the south and ambiguous results in the north. In the present study, we use data from the first 39 Juno perijoves to reexamine this question. We find a dusk region 2.9 to 5.5 times more powerful than the dawn one, in qualitative agreement with the previous study but contrary to theoretical expectations. These results support the idea that the main emissions cannot be fully described by corotation enforcement currents.