Laboratory Experiments Confirm the Polarization of Auroral Emissions

A series of experiments have shown recently that several auroral lines are polarized, when observed from the ground. However, this polarization may be caused by indirect light sources (from ground or sky) scattered in lower atmosphere Rayleigh and Lorenz-Mie scattering, during crossing ionospheric current sheets. Here, we present measurements N_{2}^+ blue (427.8 nm) purple (391.4 emissions a laboratory confined setting excludes any pollution scattering. We show both at level comparable to natural observations. Our results furthermore degree Linear Polarization depends on magnetic conditions. This set confirms controlled environnement constitutes strong evidence favor emission already polarized upper atmosphere.