title: Monte carlo studies of the sky radiation at twilight.
abstract: Results are presented in several wavelengths of the sky intensity and polarization along the solar vertical at twilight, as calculated using the backward Monte Carlo method applied to spherical shell atmospheres. Molecular scattering with anisotropy of molecules, ozone absorption, and refraction are taken into account. The dependence of the intensity on the solar depression angle is in general agreement with calculations based upon single plus second order scattering, but the degree of polarization is much higher. It is verified that the molecular plus ozone atmosphere does not explain the purple light. The elongation of the Babinet neutral point from the sun is determined as a function of solar depression angle.
authors.forename: W G
authors.initials: WG
authors.lastname: Blättner
authors.forename: H G
authors.initials: HG
authors.lastname: Horak
authors.forename: D G
authors.initials: DG
authors.lastname: Collins
authors.forename: M B
authors.initials: MB
authors.lastname: Wells