Shapes and centre-to-limb variation of the H and K lines in sunspot umbrae

Abstract

The shapes of the Ca ii H and K lines in sunspot umbral spectra vary from single asymmetric peaks near the centre of the disk to almost symmetric double peaks at the limb. In addition, there are other differences in the behaviour of both H and K lines in sunspots compared to the quiet Sun. The whole complex of the phenomena observed can not be explained by large scale chromosphere motions. Instead, a satisfactory model reproducing in detail peculiarities of the umbral emission reversals contains a cloud of emitting and absorbing gas located above the chromosphere, which flows into the sunspot. The radiation field parameters in such a cloud are consistent with the concept of weak quiescent prominences above the umbra.

The energy of waves in the photosphere and lower chromosphere

“…Both lines have thus been used intensively for studies of the chromosphere, where useful spectral lines are scarce. Ground-based observations are mainly limited to Ca ii H and K (e.g., Jensen & Orrall 1963;Beckers 1968;Liu 1974;Teplitskaia & Firstova 1976;Cram & Dame 1983;Rutten & Uitenbroek 1991;Lites et al 1999;Rezaei et al 2007;Beck et al 2008b;), Hα (e.g., Bray 1973Schmieder et al 1984;Tsiropoula et al 1993;Balasubramaniam et al 2004;López Ariste et al 2005;Sánchez-Andrade Nuño et al 2008;Cauzzi et al 2009;Bostancı 2011), the Ca ii IR triplet (e.g., López Socas-Navarro 2005;Pietarila et al 2007b;Cauzzi et al 2008;Vecchio et al 2009), and He i…”

The energy of waves in the photosphere and lower chromosphere: III. Inversion setup for Ca II H spectra in local thermal equilibrium

“…Both lines have thus been used intensively for studies of the chromosphere, where useful spectral lines are scarce. Ground-based observations are mainly limited to Ca ii H and K (e.g., Jensen & Orrall 1963;Beckers 1968;Liu 1974;Teplitskaia & Firstova 1976;Cram & Dame 1983;Rutten & Uitenbroek 1991;Lites et al 1999;Rezaei et al 2007;Beck et al 2008b;, Hα (e.g., Bray 1973;Schmieder et al 1984;Tsiropoula et al 1993;Balasubramaniam et al 2004;López Ariste et al 2005;Sánchez-Andrade Nuño et al 2008;Cauzzi et al 2009;Bostancı 2011), the Ca ii IR triplet (e.g., López Socas-Navarro 2005;Pietarila et al 2007b;Cauzzi et al 2008a;Vecchio et al 2009), and He i at 1083 nm (Lites 1986;Rüedi et al 1995;Socas-Navarro & Elmore 2005;Sánchez-Andrade Nuño et al 2007;Kuckein et al 2009;Felipe et al 2010) by the absorption in the Earth's atmosphere, whereas from space also Mg ii h and k, Lα, and other lines in the extreme UV are accessible (e.g., Kneer et al 1981;Bonnet 1981;Fontenla et al 1988;Curdt et al 2010) 1 .…”