Diffraction patterns produced by a total solar eclipse as a possible cause of the "shadow band" phenomenon

Abstract

Faint patterns of light and shadow known as "shadow bands" are often seen for a few moments before, and for a similar period Just after, a total solar eclipse. The cause of these bands is not known at this time. One of the proposed mechanisms for producing these shadow bands is basic Fresnel edge diffraction.A computer program was developed by the writer to calculate the Fresnel patterns produced by the eclipse geometry. Certain assumptions, believed to be reasonable, were made in this development. The resulting patterns were compared to the available data on shadow bands, and were found to differ by roughly two orders of magnitude in most respects.The author concludes that basic Fresnel edge diffraction for visible wavelengths is not capable of producing shadow band like patterns.