Possible Origins of the 12µ Emission Lines in the Solar Spectrum

Braut and Noyes (1982,1983) have reported the detection of about 40 unidentified emission lines near 12µ in the solar spectrum. The strongest lines, at 811.578 cm-1 and 818.062 cm-1, respectively, appear as broad, shallow absorption lines, less than 3% deep, with central, emission reversals projecting 5-10% above the continuum. The emission lines strengthen at the limb and over spot penumbrae but seem to be absent over spot umbrae. The full width at half-intensity of the emission lines is about 5 km/sec, but the absorption widths are more than 10 times as broad. Over spot penumbrae, the Zeeman splitting of the emission lines is striking. The lines have the appearance of a Zeeman triplet; the central component is nearly absent at the center of the disk but is very strong near the limb where the field is viewed perpendicularly to the line of sight. The splitting over spot penumbrae is about 10 times the width of the central component, and is consistent with that of a spectral line with a Landé g-factor of unity in a magnetic field of 1500 gauss. Braut and Noyes (1982, 1983) point out that the 12 u lines are a potentially powerful tool for magnetic field measurements in stars. Further observational details will be found in their referenced papers.