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Astron. Astrophys. 341, 264-274 (1999)

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Wavelength shifts of emission line profiles due to velocity fields in the solar corona

R. Ventura and D. Spadaro

Osservatorio Astrofisico di Catania, CNR-Gruppo Nazionale di Astronomia, UdR di Catania, Città Universitaria, Viale A.Doria 6, I-95125 Catania, Italy

Received 2 December 1997 / Accepted 29 April 1998

Abstract

We have investigated the dependence of the wavelength shift of the coronal emission line profiles on the line of sight velocity of the emitting plasma.

The results of our numerical calculations point out that, while the wavelength shift of the collisionally excited component of the line is related to the line of sight velocity by the usual formula for the Doppler effect, that of the resonantly scattered component also depends on the angle of scatter and on the angle between the velocity vector and the line of sight.

For the same outflow velocity, the absolute value of the resonantly scattered component shift is significantly smaller than that of the collisional component. Since both mechanisms generally contribute to the formation of a coronal line, we conclude that the results of this work should be taken into account when deducing line of sight velocities from the analysis of emission line profiles observed in the extended solar corona.

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

Send offprint requests to: rventura@alpha4.ct.atro.it

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© European Southern Observatory (ESO) 1999

Online publication: November 26, 1998
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