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Astron. Astrophys. 335, 323-328 (1998)

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Oscillations of the Sun's chromosphere

VIII. Horizontal motions of Ca II K bright points

S. Wellstein 1, F. Kneer 1 and M. von Uexküll 2

1 Universitäts-Sternwarte, Geismarlandstrasse 11, D-37083 Göttingen, Germany
2 Kiepenheuer-Institut für Sonnenphysik, Schöneckstrasse 6, D-79104 Freiburg, Germany

Received 24 November 1997 / Accepted 24 March 1998


We present a re-analysis of a time series of solar disc centre Ca II [FORMULA] filtergrams taken with the Vacuum Tower Telescope at the Observatorio del Teide/Tenerife. We concentrate on the measurements of proper motions of K grains in the internetwork regions and of bright points in the chromospheric network. For the K grains we find horizontal velocities of 2-15 km s-1, values much lower than those deduced by Steffens et al. (1996) from a smaller sample, analyzed differently. In accord with our earlier conclusion from k-[FORMULA] diagrams (Kneer & von Uexküll 1993) and with numerical simulations by Carlsson & Stein (1997) high-frequency (pseudo-) p-modes can viably explain the K grains. Yet, the rareness of the K grains may indicate a connection to magnetic fields. The proper motions of the network bright points are non-periodic, very impulsive, with velocities of 7-10 km s-1. Estimating the energy flux if these motions are magnetic kink waves (cf. Choudhuri et al. 1993, Muller et al. 1994), we find it sufficient to heat the solar corona, but too small to cover the radiative losses of the chromospheric network.

Key words: Sun: chromosphere – Sun: oscillations

Send offprint requests to: F. Kneer

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© European Southern Observatory (ESO) 1998

Online publication: June 12, 1998