Spectroscopic Studies of the Solar Corona I. Spatial Variations in Line Parameters of Green and Red Coronal Lines

Abstract

We obtained simultaneously profiles of the coronal green line (FeXIV 5303 A) and red line ([FeX] 6374 A) on a number of days at several regions covering an area of about 200″ × 500″ in the solar corona. The intensity, velocity, and width for both of these lines were computed by making a Gaussian fit to the observed line profile. We find that in coronal structures the spatial variations in the red and green line intensities are correlated. The ratio of green- to red-line intensities varies between 0.6–9.2 for different coronal structures. The value of the intensity ratio in an individual coronal structure also varies with height above the solar limb along the structure. The range of values of the intensity ratio observed implies that most of the structures under investigation had a temperature in the range of 1.2–1.6 × 106 K. Also, we find that in coronal structures the width of the red line increases with height above the limb, whereas the green-line width in the same region decreases with height. This behavior of the line widths can be explained if we assume the mixing of plasma in the middle and higher portions of the coronal structures by microturbulence or traveling waves, which have been detected recently. No Ha loops and activity were seen in these regions during the observation periods.