Jupiter's polar ionospheric flows: High resolution mapping of spectral intensity and line-of-sight velocity of H3+ ions

We present a detailed study of the H+3 auroral emission at Jupiter, which uses data taken on 31 December 2012 with the long-slit echelle spectrometer Cryogenic Infrared Echelle Spectrograph (European Southern Observatory's Very Large Telescope). The entire northern auroral region was observed using significantly more slit positions than previous studies, providing a highly detailed view of ionospheric flows, which were mapped onto polar projections. Previous observations of ionospheric flows in Jupiter's northern auroral ionosphere, using the long-slit echelle spectrometer CSHELL (NASA Infrared Telescope Facility) to measure the Doppler-shifted H+3 ν2 Q(1,0−) line at 3.953 μm, showed a strongly subrotating region that was nearly stationary in the inertial magnetic frame of reference, suggesting an interaction with the solar wind. In this work, we observe this stationary region coincident with a polar region with very weak infrared emission, typically described as the dark region in UV observations. Although our observations cannot determine the exact mechanisms of this coupling, the coincidence between solar wind controlled ionospheric flows and a region with very low auroral brightness may provide new insights into the nature of the solar wind coupling. We also detected a superrotating ionospheric flow measured both at and equatorward of the narrow bright portion of the main auroral emission. The origin of this flow remains uncertain. Additionally, we detect a strong velocity shear poleward of the peak in brightness of the main auroral emission. This is in agreement with past models which predict that conductivity, as well as velocity shear, plays an important role in generating the main auroral emission.