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

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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 2

1 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


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


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© European Southern Observatory (ESO) 1997

Online publication: May 26, 1998