Letter to the Editor

Oscillations in the wings of sunspot transition region lines

¹ Institute of Theoretical Astrophysics, University of Oslo, PO Box 1029 Blindern, 0315 Oslo, Norway e-mail: nils.brynildsen@astro.uio.no;per.maltby@astro.uio.no;olav.kjeldseth-moe@astro.uio.no
² Max-Planck-Institut für Aeronomie, 37191 Katlenburg-Lindau, Germany e-mail: wilhelm@linmpi.mpg.de

Corresponding author: P. Maltby, per.maltby@astro.uio.no

Received: 4 November 2002
Accepted: 15 December 2002

Abstract

We explore a new approach to the investigation of optically thin emission lines by comparing the intensity variations in opposite wings of the spectral lines and apply the method to investigate the oscillations above sunspots. The observations show that it is easier to detect the 3 min oscillations above sunspots in the short wavelength (“blue”) wing than in the long wavelength (“red”) wing of the lines. The observed oscillations are compatible with the spectral line signatures of upwardly propagating acoustic waves.