Spectroscopic Studies of the Solar Corona II. Properties of Green and Red Emission Lines in Open and Closed Coronal Structures

Abstract

Abstract We obtained profiles of the green (Fe XIV 5303 Å) and red (Fe X 6374 Å) emission lines simultaneously on 1998 July 18–19 for about 4 hours with a cadence of 10 minutes, covering an area of about $ 200'' \times 500''$ in the solar corona. The line width (FWHM), intensity, and Doppler shift for both lines were computed using Gaussian fits to the observed line profiles. We then studied any systematic differences in these parameters between closed and open field structures, and their time variations. The derived line widths indicate that the FWHM of the red line increases with height above the limb at a rate of $ 0.5 \hbox{--} 2.6 \,\mathrm{m}$ Å$ \,\mathrm{arcsec}^{-1}$ and the green-line width decreases with height at a rate of $ 1.2 \hbox{--} 3.4 \,\mathrm{m}$ Å$ \,\mathrm{arcsec}^{-1}$. The difference in the time-averaged values of the widths of the green line in open and closed coronal structures at a given height above the limb is small, whereas the width of the red line in open structures is substantially larger than that in the closed loop-like coronal structures.