Polarization Singularities in the Clear Sky
NAVAL ACADEMY ANNAPOLIS MD DEPT OF PHYSICS
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Ideas from singularity theory provide a simple account of the pattern of polarization directions in daylight. The singularities two near the Sun and two near the anti-Sun are points in the sky where the polarization line pattern has index 12 and the intensity of polarization is zero. The singularities are caused by multiple scattering that splits into two each of the unstable index 1 singularities at the Sun and anti-Sun, which occur in the single-dipole scattering Rayleigh theory. The polarization lines are contours of an elliptic integral. For the intensity of polarization unnormalized degree, it is necessary to incorporate the strong depolarizing effect of multiple scattering near the horizon. Singularity theory is compared with new digital images of sky polarization, and gives an excellent description of the pattern of polarization directions. For the intensity of polarization, the theory can reproduce not only the zeros but also subtle variations in the polarization maxima.
- Atmospheric Physics