Interpretation of infrared oxygen spectroheliograms

Spectroheliograms have been obtained in the line cores of two infrared multiplets of neutral oxygen. Those made in the lines of the 7770 Å multiplet show a very smooth intensity distribution, with faculae and sunspot penumbrae at a very low contrast with respect to the undisturbed photosphere. Spectroheliograms made in the core of 8446.37 Å show evidence of coupling with chromospheric features and of blending with a line of neutral iron.An analysis of a 7772 Å spectroheliogram indicates that a magnetic field of approximately 1500 G is required to produce the disappearing penumbra phenomenon. This value is consistent with the recent observations of Beckers and Schröter (1969).