SHADOW BANDS DURING THE TOTAL SOLAR ECLIPSE OF 11 JULY 1991

We recorded shadow bands just before and just after the total phase of the solar eclipse of 11 July 1991. The recordings were made using two broad band silicon photodiodes separated horizontally by 100 mm. They faced the zenith, near to where the eclipsed Sun lay as seen from our observing site close to San Jose del Cabo in Baja California. The irradiance fluctuations associated with the shadow bands were around 0.04 W m-2 peak to peak on a background of 1-3 W M-2. The cross-correlation function indicates that the shadow bands were moving at about 1.8 m s-1 perpendicular to their extent. The power spectral density functions are in accord with the shadow band theory Of CODONA [(1986), Astron. Astropkys. 164, 415-427].