Astron. Astrophys. 324, 381-394 (1997)

Fe XVII X-ray lines in solar coronal and laboratory plasmas

K.J.H. Phillips ¹, C.J. Greer ², A.K. Bhatia ³, I.H. Coffey ², R. Barnsley ⁴ and F.P. Keenan <sup>2

1</sup> Astrophysics Division, Rutherford Appleton Laboratory, Chilton, Didcot, Oxon. OX11 0QX, UK (phillips@solg2.bnsc.rl.ac.uk)
² Department of Physics, The Queen's University, Belfast BT7 1NN, Northern Ireland, UK
³ Laboratory for Astronomy and Solar Physics, NASA Goddard Space Flight Center, Greenbelt, MD 20771, USA
⁴ Department of Physics and Astronomy, Leicester University, Leicester LE1 7RH, UK

Received 27 September 1996 / Accepted 2 January 1997

Abstract

Theoretical intensities of the Fe XVII X-ray lines due to transitions (near 15 Å) and (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 , 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 . We find very satisfactory correspondence between solar spectra and synthetic spectra based on calculated line intensities with appropriately chosen 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 and 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 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.

Key words: atomic data atomic processes Sun: activity Sun: flares Sun: X-rays, gamma rays

Send offprint requests to: K.J.H. Phillips

Contents

• 1. Introduction
• 2. Atomic data
• 3. Synthetic spectra and diagnostic potential
• 4. Observed spectra and comparison with theory
  • 4.1. Solar active region and flare spectra
  • 4.2. Tokamak spectra
• 5. Summary
• Acknowledgements
• References

© European Southern Observatory (ESO) 1997

Online publication: May 26, 1998

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