Abstract
A Study of Spectroheliograms.—An important contribution to the study of the sun's atmosphere by means of spectroheliograms, which record the sun's surface in monochromatic light at different levels from the photosphere to the top of the chromosphere, is given by L. D'Azambuja in Annales de l'Obseroatoire de Paris, Section d'Astrophysique, à Meudon, Tome 8, Fas. 2. Hitherto most spectroheliograms have been obtained in the hydrogen light (Ha) and in that of ionised calcium (H and K), though Deslandres in 1894, Hale and Ellerman in 1903, and Fox in 1905 first respectively recorded the sun's surface in the light of other elements. D'Azambuja's present research is concerned chiefly with such elements as magnesium, iron, calcium (neutral), sodium, and strontium, that are characteristic of the lower chromosphere or reversing layer. For this work a powerful spectroheliograph such as that at Meudon is essential, and it was possible to study the changes as the narrow selecting slit was set respectively at the middle and at the edge of the spectral line used. As is well known, there are significant differences (explicable as being mainly due to difference of level in the sun's atmosphere) between spectroheliograms taken in the light which comes from the narrow central portion of the Ha, H, or K lines and those obtained when the edges of the lines are likewise isolated. A comparison of these established differences with those observable in the case of the lines due to lower-lying elements, together with a knowledge of the curves of intensity of the lines, forms the basis of the present discussion.
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Our Astronomical Column. Nature 126, 821 (1930). https://doi.org/10.1038/126821a0
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DOI: https://doi.org/10.1038/126821a0