[1987] J. Opt. Soc. Am. A 4, 601-608, doi:10.1364/JOSAA.4.000601
G. P. Können

The polarization distribution in the sky during a total solar eclipse is calculated with a simple secondary light scattering model. The model can explain various observations during totality, including the measurements by Shaw of the polarization distribution of the sky in the solar vertical during the 1973 total eclipse.