Monday

We present results that indicate the existence of two distinct neutral heating processes associated with a discrete auroral arc over Svalbard: a heavily asymmetric temperature increase, observed over a large altitude range, directly adjacent to the arc structure on its poleward edge only; and a varying temperature increase, seen within the arc itself, constrained to a narrow altitude range close to the mesopause. By utilising a range of observations and new analysis methods we are able to measure the atmospheric temperature profile, over auroral altitudes, at unprecedented temporal and spatial scales. The University of Southampton's Auroral Structure and Kinetics (ASK) instrument and the ESR (EISCAT Svalbard Radar) are used to measure precipitating particle energies and fluxes for the event in question. These parameters are used as an input to the Southampton ionospheric model to retrieve N2 volume emission rate profiles for the duration of the event. The University's complementary instrument HiTIES (High Throughput Imaging Echelle Spectrograph) records high resolution emission spectra of the aurora, which are then fit with a synthetic N2 spectra, generated with the modeled N2 volume emission rate profiles and a library of trial temperature profiles. The application of this technique allows us to produce a time series of best fit neutral temperature profiles and thus to distinguish between temperature changes due to variation in emission altitude and those due to localised heating associated with the arc’s electrodynamics.