The broad-band circular polarization of sunspots, 0.37-4.5 microns

Abstract

Sunspot circular polarization was examined with a sensitivity exceeding 3 millionths over the range 3700 A to 4.5 microns. Spectropolarimetric scans were performed with an aperture of 10 arcsec to determine the spatially averaged wavelength dependencies. A slow scan was also undertaken of the Ca II H and K lines. Passbands of at least 0.1 micron width were examined. The V value was found to be particular for each sunspot. A continuum magneto-opacity model was found to produce fits to the magnitude, sign, and approximate spectral shape of sunspot V values at wavelengths of at least l.5 micron. However, excessive UV values were observed and correlation with line blanketing was indicated. It is suggested that the effect was produced by atomic magneto-emission oriented by anisotropic radiation.