Electron densities in the solar atmosphere from EUV emission lines

Abstract

The solar EUV emission lines from boron-like (Mg VIII and Si X), carbon-like (Mg VII and Si IX) and oxygen-like (Si VII and S IX) ions have been used to derive electron densities in the solar atmosphere. The line intensity ratios using Kopp and Orrall model fall on the density-sensitive portion of the line intensity ratio curves which are therefore used as density monitors of the quiet sun and the coronal holes. The electron densities of 1.6 × 109 cm-3, 9.7 × 108 cm-3, 5.2 × 108 cm-3 and 5.1 × 108 cm-3 are estimated at the electron temperatures of 5 × 105 K, 8 × 105 K, 106 K and 1.6 × 106 K, respectively for the quiet Sun whereas the corresponding electron densities of 7.4 × 108 cm-3, 4.8 × 108 cm-3, 2.6 × 108 cm-3 and 1.8 × 108 cm-3 for the coronal holes. The EUV emission lines, used in this study and which are hitherto not observed, have sufficient intensity for observation by future solar missions. © 1989.