Auroral and Non-Auroral H3+ ion winds at Uranus with Keck-NIRSPEC and
IRTF-iSHELL
Abstract
To date, no investigation has documented ionospheric flows at Uranus.
Previous investigations of Jupiter and Saturn have demonstrated that
mapping ion winds can be used to understand ionospheric currents and how
these connect to magnetosphere-ionosphere coupling. We present a study
of Uranus’s near infrared emissions (NIR) using data from the Keck II
Telescope’s Near InfraRed SPECtrograph (NIRSPEC) and the InfraRed
Telescope Facility’s iSHELL spectrograph. H3+ emission lines were used
to derive dawn-to-dusk intensity, ionospheric temperatures and ion
densities to identify auroral emissions, with their Doppler shifts used
to measure ion velocities. We confirm the presence of the southern NIR
aurora in 2016, driven by elevated H3+ column densities up to 6.0 x 1016
m-2. While no auroral emissions were detected in 2014, we find a 14% to
20% super rotation across the planet’s disk in 2014 and a 7% to 18%
super rotation in 2016.