We compute a new grid of plage models to determine the difference in temperature versus mass column density structure T(m) between plage regions and the quiet solar chromosphere, and to test whether the solar chromosphere is geometrically thinner in plages. We compare partial redistribution calculations of Mg ii h and k and Ca ii K to NRL Skylab observations of Mg ii h and k in six active regions and Ca ii K intensities obtained from spectroheliograms taken at approximately the same time as the Mg ii observations. We find that the plage observations are better matched by models with linear (in log m) temperature distributions and larger values of m0 (the mass column density at the 8000 K layer in the chromosphere), than by models with larger low chromosphere temperature gradients but values of m0 similar to the quiet Sun. Our derived temperature structures are in agreement with the grid originally proposed by Shine and Linsky, but our analysis is in contrast to the study by Kelch which implies that stellar chromospheric geometrical thickness is not affected by chromospheric ‘activity’. We conclude that either the stellar Mg ii observations upon which the Kelch study was based are of poorer quality than had been assumed, or that the spatial averaging of inhomogeneous structures, which is inherent in the stellar data, does not lead to a best fit one-component model similar in detail to that of a stellar or a solar plage.

view Abstract Citations (12) References (24) Co-Reads Similar Papers Volume Content Graphics Metrics Export Citation NASA/ADS Sodium Line Formation in Arcturus. II. The Use of Empirical and Opacity Sampling Models and the Nature of Partial Redistribution Effects Kelch, Walter L. ; Milkey, Robert W. Abstract In a previous paper, we presented calculations of departure coefficients, D line profiles, and subordinate line strengths for sodium lines in Arcturus using a model atmosphere calculated with straight mean opacities. This paper presents results of similar calculations using an empirical model of Arcturus inferred from the Ca ii H and K lines and a model atmosphere calculated by the opacity sampling method. We also compare partial redistribution calculations of the D2 line profile to the complete redistribution profile. We find that the partial redistribution D2 profile has deeper core and inner wing regions and slightly shallower outer wings. We also find that the partial redistribution calculation may affect the strengths of certain subordinate transitions. Subject headings: line formation - radiative transfer - stars: atmospheres - stars: individual Publication: The Astrophysical Journal Pub Date: September 1976 DOI: 10.1086/154623 Bibcode: 1976ApJ...208..428K full text sources ADS |