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Astron. Astrophys. 362, L49-L52 (2000)

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Letter to the Editor

On the relationship between shift and intensity of ultraviolet lines in coronal holes and the quiet Sun

K. Stucki 1, S.K. Solanki 2, U. Schühle 2 and I. Rüedi 3

1 ETH-Zentrum, Institute of Astronomy, 8092 Zürich, Switzerland
2 Max-Planck-Institut für Aeronomie, 37191 Katlenburg-Lindau, Germany
3 PMOD/WRC, 7260 Davos Dorf, Switzerland

Received 20 July 2000 / Accepted 26 September 2000

Abstract

We study the relationship between wavelength shifts and intensities of chromospheric, transition-region and coronal ultraviolet emission lines in polar coronal holes and in the normal quiet Sun using SUMER data. Within coronal holes almost all the lines showing the network and formed above 30 000 K show a correlation between blueshifts and brightness. This extends and supports the conclusion reached by Hassler et al. (1999) that the fast solar wind emanates from the network. In the normal quiet Sun, however, we find that only lines formed above [FORMULA] K show such a trend, the cooler lines being more redshifted in the network. This suggests that either there is a fundamental difference in the initial acceleration of the solar wind in coronal holes and the normal quiet Sun, or that the wavelength-shift versus brightness relationship in the quiet Sun stems from other processes or structures (loops) than in coronal holes (open field lines).

Key words: Sun: corona – Sun: solar wind – Sun: transition region – Sun: UV radiation

Send offprint requests to: K. Stucki

Correspondence to: kstucki@astro.phys.ethz.ch

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© European Southern Observatory (ESO) 2000

Online publication: October 30, 2000
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