In green, the observations of the polarisation flux (top), DoLP (middle), and AoLP (bottom) at 557.7 ± 5 nm over 7 almucantars on February 27, 2020. The thickness indicates the uncertainties). A sliding average of 10 s is applied. Black stars (★): Contribution of the ground emissions G. Red plus (+): Contribution of the sky emission and its reflection on the snow S. Pink (Y): Linear combination of the ground and sky contributions that best fits the flux variations. Blue crosses (×): Direct light only (i.e., not scattered in the atmosphere, no other sources that could be scattered by the atmosphere are taken into account) with a polarisation at the emission (here d_max = 5% and the electrons motion direction is 50° azimuth and −20° elevation). The dashed vertical black line indicates the direction of Skibotn. The picture of the sky at 557.7 nm at the time of the observation is shown in Appendix A.