  Throughout 2017, the Hubble Space Telescope (HST) observed the northern
far-ultraviolet aurorae of Saturn at northern solstice, during the Cassini
Grand Finale. These conditions provided a complete viewing of the northern
auroral region from Earth and a maximal solar illumination, expected to
maximize the ionosphere-magnetosphere coupling. In this study, we analyze 24
HST images concurrently with Cassini measurements of Saturn's Kilometric
Radiation and solar wind parameters predicted by two MHD models. The aurorae
reveal highly variable components, down to timescales of minutes, radiating 7
to 124 +/-11 GW. They include a nightside-shifted main oval, unexpectedly
frequent and bright cusp emissions and a dayside low latitude oval. On average,
these emissions display a strong Local Time dependence with two maxima at dawn
and pre-midnight, the latter being newly observed and attributed to nightside
injections possibly associated with solstice conditions. These results provide
a reference frame to analyze Cassini in situ measurements, whether simultaneous
or not.
