Considering the polarization of the oxygen thermospheric red line for space weather studies

Abstract

Space weather thermospheric monitoring requires real‐time and large‐scale measurements. In order to monitor the thermospheric variations due to geomagnetic activity, one relies mostly on the measurements of the intensity of the atomic oxygen green line and on the indirect measurement of the total electron content. These two parameters do not allow retrieving the full characteristics of the thermosphere, and a third proxy is required, for example, in orbitography. We propose to use the polarization of the atomic oxygen red line to fulfill this requirement. The first measurements of the polarization of thermospheric nightglow lines have been performed in the first part of the twentieth century and especially during the last International Geophysical Year. Amongst the oxygen visible lines, only the red one seems to be potentially polarized. However, there exists a disagreement between the different measurements. At the origin of the polarization, there is always a dissymmetric mechanism. It triggers either an emission process, a light scattering, or, in the case of the oxygen red line, a collision mechanism. This paper reviews the different experiments performed in the past and proposes to explore this matter with modern facilities. If successful, this investigation could lead to a systematic reanalysis of the previous red line interferometric measurements.