EUV spectral lines from solar wind source regions: The resonance doublets of N V, MG X and SI XII, and the Fe XII λ1242 forbidden line.

Abstract

We present numerical simulations of intensities and profiles of the N V λ1239 and λ 1243, Mg X λ610 and λ625, Si XII λ499 and λ521, and Fe XII λ1242 lines expected from an equatorial and polar coronal hole at solar minimum, when observed on the plane of the sky in the 1.2R_sun_-8R_sun_ range of heliocentric distance. The radial variations of coronal temperatures, densities and outflow speeds inside these structures are those determined by Withbroe (1988) through a one-fluid steady-state radiative energy balance model. We discuss how the spectral features depend on the physical parameters of the examined structures, in order to evaluate to which extent they can put constraints on empirical models of the extended corona. We also investigate the effects of the deviations from ionization equilibrium occurring in the plasma outflowing from the considered coronal structures on the intensity and profile of the spectral lines examined. Such effects become significant at heliocentric distances higher than 3R_sun_. These results may contribute to prepare and interpret UVCS/SOHO future observations.