Auroral electrodynamics and Joule heating studied through high-resolution multi-spectral optical observations of the aurora

The aurora often contains rapid dynamics on fine scales, down to 10s of metres perpendicular to the magnetic field. This structuring and dynamics is a signature of the magnetosphere-ionosphere coupling processes and auroral acceleration above the ionosphere. High-resolution observations of the aurora provide a powerful key to access the physics of these processes, and to understand the impact of the auroral energy deposition in the neutral atmosphere. The Auroral
Structure and Kinetics (ASK) instrument, operated by the University of Southampton and KTH, has now been observing aurora above Svalbard for many years, and the Universities of Southampton and Northumbria have recently installed a new ASK-like instrument called Embla in Skibotn, Norway, close to the EISCAT_3D radar. These instruments image the
aurora at high spatial (20 m) and temporal (32 Hz) resolution using multiple synchronised cameras. Through a careful choice of optical filters, we are able to simultaneously measure the energy and flux of electron precipitation, ionospheric electric field, and neutral temperature in aurora. Observations reveal extremely large and dynamic electric fields and rapid neutral temperature changes in the vicinity of aurora. I will present examples of the wide variety of auroral
structuring and dynamics observed, some things we understand about their generation mechanisms, and also highlight some open questions.