Physical properties of solar chromospheric plages

✍ Scribed by Walter L. Kelch; Jeffrey L. Linsky

• Publisher: Springer
• Year: 1978
• Tongue: English
• Weight: 484 KB
• Volume: 58
• Category: Article
• ISSN: 0038-0938
• DOI: 10.1007/bf00152553

✦ Synopsis

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 mo (the mass column density at the 8000 K layer in the chromosphere), than by models with larger low chromosphere temperature gradients but values of mo aimilar 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.