Prominence and quiet-Sun plasma parameters derived from FUV spectral emission^*

¹ Royal Observatory of Belgium, 3 Av. Circulaire, 1180 Bruxelles, Belgium e-mail: s.parenti@oma.be
² Institut d'Astrophysique Spatiale, Bât. 121, Université Paris Sud-CNRS, 91405 Orsay, France

Received: 30 January 2007
Accepted: 21 March 2007

Abstract

Context.A solar prominence and the quiet-Sun (QS) were observed with SOHO/SUMER in October 1999. With this dataset we built the first comprehensive UV spectral atlas in the range 800–1250 Å for a prominence, thus complementing the existing reference atlases for the QS.

Aims.This is a detailed study based on the information in this atlas, with the aim of deriving the plasma parameters in two distinct regions. The large amount of information available allows us to establish these parameters with lower uncertainty than in previous studies, leading to reference values for theoretical investigations.

Methods.The measured lines' FWHM were used to derive the distribution of the non-thermal velocities at various temperatures. The lines intensities were used to derive the electron densities at temperatures of 7 10⁴  K and the differential emission measure.

Results.The comparison with the QS shows lower velocities in the prominence for temperature T with 5.4. The velocities derived in the highest part of the prominence show a lower gradient with the temperature. The value obtained for the electron density indicates a low pressure prominence. We conclude with a discussion of the energy budget in the prominence.