Meso-scale observations of Joule heating near an auroral arc and ion-neutral collision frequency in the polar cap E-region

We report on the first meso-scale combined ionospheric and thermospheric observations, partly in the vicinity of an auroral arc, from Svalbard in the polar cap on 2 February 2010. The EISCAT Svalbard radar employed a novel scanning mode in order to obtain F- and E-region ion flows over an annular region centred on the radar. Simultaneously, a co-located Scanning Doppler Imager observed the E-region neutral winds and temperatures around 110 km altitude using the 557.7 nm auroral optical emission. Combining the ion and neutral data permits the E-region Joule heating to be estimated with an azimuthal spatial resolution of ~64 km at a radius of ~163 km from the radar. The spatial distribution of Joule heating shows significant meso-scale variation. The ion-neutral collision frequency is measured in the E-region by combining all the data over the entire field of view with only weak aurora present. The estimated ion-neutral collision frequency at ~113 km altitude is in good agreement with the MSIS atmospheric model.