Polarization of the green-line corona on July 11, 1991 solar eclipse

High quality photographic polarized images of the green-line lambda 530.3 nm corona were obtained during the July 11, 1991 solar eclipse by using a narrow-band 0.17 nm interference filter. Image processing allowed us to derive the green-line polarization within the range 1.08 - 1.40 R.. The corresponding degrees of polarization p vary from 0% up to about 30% in different coronal regions. At equatorial latitudes p varies from 0% to 15%, while in the brightest coronal regions it does not exceed 5%. In regions of observed high-latitude white-light coronal streamers, the green-line polarization gradually increases with distance from 10% to about 30%. Anticorrelation between the degree of polarization and the green-line corona intensity was found in analysing the entire data matrix. It seems that this finding in itself contains information about the role of electron collisions in the excitation of the green line, and about certain physical properties of the coronal magnetic field.