Density sensitivity of the solar EUV emission from boron-like ions

The paper investigated the level populations and the line emission arising from ions of the boron isoelectronic sequence from C II to Ca XVI. It is found that, under conditions present in the solar corona, some of these ions have pairs of emission lines having intensity ratios which are density-sensitive. The boron-like lines observed in the solar spectrum between 300 and 1350 A are analyzed, and densities for quiet and active regions, coronal holes, sunspots, and flares are derived. Some aspects of the differences in the behavior of the emission from the lithium and boron sequences are also discussed.