FeXVII X-ray lines in solar coronal and laboratory plasmas

Theoretical intensities of the Fe xviiX-ray lines due to transitions 2p6 − 2p53d (near 15 Å) and 2p6 − 2p53s (near 17 Å) are presented, and compared with solar flare and active region spectra. The ratio of the 15 Å lines to the 17 Å lines is a function of temperature Te, but for solar spectra this is not of practical use because of the resonance scattering of the intense 15.015 Å line. Instead we use the ratio of a nearby Fe xviii line to obtain Te. We find very satisfactory correspondence between solar spectra and synthetic spectra based on calculated line intensities with appropriately chosen Te apart from the 15.015 Å line, which is sometimes less intense than its theoretical value, apparently owing to resonance scattering. Spectra emitted by DITE and JET tokamak plasmas with measured Te and Ne are also considered. A predicted density variation of the ratio of the Fe xvii lines at 17.051 Å and 17.096 Å is confirmed, and using Abel inversion techniques applied to a sequence of DITE spectra with different radial distances good agreement is found between the theoretical temperature variation of the I(15.015 Å)/I(16.776 Å) line ratio and that derived from these spectra.We conclude that our calculated Fe xvii line intensities are very reliable and may therefore be used in future analysis.