Green-line polarization observations of the solar corona and their interpretation

Polarization observations in the lambda 5303 Angstrom FeXIV line during the eclipse of July 11, 1991 are presented. A new polarization map probing somewhat greater heights in the corona is constructed, and the distribution of polarization position angles is given. Low degrees of polarization p are obtained ill the equatorial regions; at low heights, they are consistent with the results of out-of-eclipse observations. The values for p ale higher in regions of high-latitude streamers, and increase substantially with distance from the limb. The method used in the analysis made it possible to separate the line emission into two components (associated with excitation due to electron collisions and with resonant scattering of the photospheric radiation), and also to estimate the density and overall extent of the emitting region. The observed values of p ale consistent with current ideas about the corona if the relative density of the FeXIV ion is 2 x 10(-5) and the rate of excitation by electron collisions is 5 x 10(-9) cm(3)/s. The possible role of magnetic fields is briefly discussed.