Visual Measurements of the Polarization of the Solar Corona

• Main Author: Johnson, Josef Jerome
• Format: Others
• Published: 1935
• Online Access: https://thesis.library.caltech.edu/3465/1/Johnson_jj_1935.pdf; Johnson, Josef Jerome (1935) Visual Measurements of the Polarization of the Solar Corona. Dissertation (Ph.D.), California Institute of Technology. doi:10.7907/FBFH-ER25. https://resolver.caltech.edu/CaltechETD:etd-09112007-075222 <https://resolver.caltech.edu/CaltechETD:etd-09112007-075222>

<p>Visual polarization measurements were made at the eclipse of February 14, 1934, with a modified Lyot-type polarimeter attached to a four-inch equatorially-mounted refractor. The objective was stopped down to 1 1/2 inches to reduce polarization effects the instrument. Distances from the moon's limb were measured by means of a cross-wire reticle in the focal plane of the eyepiece.</p> <p>Five different points of the corona were investigated, all lying directly off the east limb of the sun and ranging in distance from the limb from 1 to 8.5 minutes of arc. The observed polarization rose rapidly from 17% at 1' to 26% at 4', remaining sensibly constant from 4' outward.</p> <p>These values are considerably higher than those previously obtained by visual methods, but are lower than the values obtained photographically. Subject to confirmation at a future eclipse, these values will constitute important evidence in favor of Schwarzschild's theory that a large part of the light of the corona is due to the scattering of photospheric light by free electrons.</p>