Red line observation in Ny Alesund on March 3, 2019. We observe at a fixed elevation of 30°, and perform 12 measures at different azimuths (North is 0, and we turn clockwise to the East by steps of 30°). In black are shown the raw data along with the associated error bars in grey, and in red the smoothed data over 15 s. From top to bottom: the observed intensity (in mV), the DoLP (in %) and the AoLP (in degrees). We also show, superimposed with the AoLP, the apparent angle of the magnetic field lines (cyan stars) and the expected AoLP for scattered light for a artificial source point in Ny Alesund, North of the instrument (pink stars).