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Abstract:
Recent observations with spectro-photo-polarimeters have shown that the auroral emissions from oxygen at 577.7 nm (green line), and from the N2+ 1st negative band emissions at 427.8 nm (blue line) and 391.4 nm (purple line) are polarized at a few percent level and that this polarization is linked to geomagnetic activity and cannot be explained by light pollution only. The origin of this polarization is still puzzling and could be related to ionospheric currents, either field-aligned or horizontal Pedersen/Hall currents.In November 2022, we set-up a multi-instrument observing campaign in Norway in order to better understand this situation. At the Skibotn observatory, we used two instruments dedicated to the measurements of auroral light polarization : PLIP, a Polar Lights Imaging Polarimeter, able to measure polarization of the three main auroral emissions (green, red and blue) on a large FOV (~44° × 30°) on the sky, and Corbel Cru, a spectro-photo polarimeter able to measure faint polarized signals in a 2° FOV in the green, blue and purple line. These data were complemented by optical observations from the ALIS_4D network in Sweden in order to obtain 2D precipitating electron fluxes using tomographic-like inversion techniques, and by radar observations with the EISCAT UHF antenna working in scanning mode. In this contribution we will present preliminary results from these instruments for a good case study obtained during this campaign. One goal of the campaign is to check whether the angle of linear polarization can be used as tracers for ionospheric currents.
