Observed heights of EUV lines formed in the transition zone and corona |
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| Authors: | George W Simon Robert W Noyes |
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| Institution: | (1) Sacramento Peak Observatory, Air Force Cambridge Research Laboratories, 88349 Sunspot, N.M., U.S.A.;(2) Smithsonian Astrophysical Observatory, Harvard College Observatory, 02138 Cambridge, Mass., U.S.A. |
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| Abstract: | The heights of formation of a number of extreme ultraviolet lines in active regions have been measured from OSO-IV spectroheliograms. Using the Lyman continuum at 2000 km above the white light limb as a reference, we find heights for Hei, Heii, Ciii, Niii, Oiv, Ovi, Neviii, Mgx, Sixii, Fexv and Fexvi that are in approximate agreement with models based on analysis of EUV emission intensities. The height of Cii is anomalously high. The accuracy of measurement is typically about 2000 km. The data suggest that the transition zone is less steep than calculated from EUV emission intensities; however, higher resolution observations are necessary to resolve the discrepancy. |
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