Letter to the Editor

Dynamic features in the solar atmosphere with unusual spectral line enhancements and Doppler-shifts

¹ Armagh Observatory, College Hill, Armagh BT61 9DG, N. Ireland e-mail: jgd@star.arm.ac.uk
² Royal Observatory of Belgium, 3 Circular Avenue, 1180 Brussels, Belgium
³ Astronomical Institute, Faculty of Mathematics, Physics and Informatics, Comenius University, Mlynská dolina, 842 48 Bratislava 4, Slovakia

Received: 16 February 2006
Accepted: 26 March 2006

Abstract

Context.The solar atmosphere contains a wide variety of transient features, here, we discuss data relating to one such feature.

Aims.To explore via simultaneous spectral and imaging data the nature of high-velocity flow events in the solar transition region.

Methods.High spectral and temporal resolution data from SUMER/SoHO plus high resolution images from TRACE are used.

Results.In the transient feature discussed, we see a factor of two enhancement in N v 1238, coupled with a factor of two decrease in O v 629 visible over 3″–4″ along the slit. Furthermore, the O v line shows a secondary component with a down-flow of ≈75 km s^-1, while the N v line shows only a small additional broadening of the line.

Conclusions.Inclusion of an electron density dependent ionization calculation will increase the N v radiance over that of O v at large electron densities. We suggest this feature can be explained via a highly focused jet at the O v/Ovi formation temperature resulting from reconnection. Also, we believe that this event is not unique but that their detection depends on the availability of simultaneous spectral and imaging data of comparable spatial and temporal resolution.