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

We have investigated the level populations and the line emission arising from ions of the boron isoelectronic sequence from C II to Ca XVI. We have 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. We have analyzed the boron-like lines observed in the solar spectrum between 300 and 1350 A and derived densities for quiet and active regions, coronal holes, sunspots, and flares. Some aspects of the differences in the behavior of the emission from the lithium and boron sequences are also discussed