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Astron. Astrophys. 332, 767-774 (1998)

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Two-dimensional spectral observations of sunspots in chromospheric lines

I. Asymmetries of Ca II lines

M.D. Ding 1, 2 and H. Schleicher 2

1 Department of Astronomy, Nanjing University, Nanjing 210093, P.R. China
2 Kiepenheuer-Institut für Sonnenphysik, Schöneckstrasse 6, D-79104 Freiburg, Germany

Received 2 January 1997 / Accepted 19 December 1997

Abstract

We present two-dimensional spectral observations of two closely located small sunspots in chromospheric lines. Line asymmetries and shifts are derived for the Ca II K line in particular. It is found that the majority of Ca II K profiles show a blue asymmetry. Red asymmetry may also appear, but only in some tiny regions. Some ephemeral blue asymmetry patches are found in the umbrae, which seem to be related to umbral flashes. On the limb side of the penumbra, the Ca II K profiles show a distinguishably blue asymmetry of K1. In contrast, the profiles on the center side are more likely to possess a blue asymmetry of K2, together with a slight red shift of K3. We discuss possible causes for such a peculiar spatial distribution of line asymmetries. Further line profile computations are needed to get a consistent and satisfactory explanation.

Key words: line: profiles – sunspots

Send offprint requests to: H. Schleicher

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© European Southern Observatory (ESO) 1998

Online publication: March 23, 1998
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