SIMULATION AND ANALYSIS OF POLLEN CORONAS

By numerical simulation of light scattering by birch and pine pollen g rains, we create color plates of coronas with vertical elliptical shap es and strong brightenings, respectively. The shape of the pollen is m odeled by the union of n ellipsoids. The Fraunhofer integral is solved by the use of the fast Hartley transform. The sensitivity of the patt erns to pollen orientation, Sun elevation, and pollen shape and size i s discussed. Good agreement is obtained with amazing photographs made by a Finnish network of amateur astonomers, in the case of strong vert ical orientation of the pollen axis.