fl194.harra_murnion02 Posted: 05-Dec-94 Updated: 22-Aug-95 Events specified: N/A
L. K. HARRA-MURNION (MSSL), K. J. H. PHILLIPS (RAL), J. R. LEMEN (LPARL), D. M. ZARRO (ARC), C. G. GREER (QUB), V. J. FOSTER (QUB), J. D. DUBAU (Meudon), I. H. COFFEY (JET), E. RACHLEW-KALLNE (Roy. Inst. Stockholm), F. P. KEENAN (QUB), A. FLUDRA (RAL), M. WILSON (RHUoL) T. WATANABE (NAOJ)
Entry for the Yohkoh Team Bulletin Board, submitted Nov. ... 1994
Theoretical X-ray spectra of helium-like sulphur (S XV) have been derived from wavelengths and intensities based on calculations using the General Relavistic Structure Package and the Dirac R-matrix code, together with Hartree--Fock calculations of dielectronic satellites. They are compared with laboratory spectra (the Alcator C and JET tokamak devices) and solar flare spectra obtained with the Yohkoh Bragg Crystal Spectrometer (BCS) and with the SMM Flat Crystal Spectrometer (FCS). The fits of the theory spectra to the observed spectra are generally in fair agreement: for the laboratory spectra, electron densities and temperatures measured by laser scattering were used for the fitted spectra, but for the solar flare spectra electron temperature was selected to give the best agreement between theory and observed spectra. The density sensitivity of the forbidden and intercombination lines of S XV should only be applicable for the higher densities (> 10^14 cm-3) of tokamak plasmas, but nevertheless a search has been made for density effects in solar flares by examining Yohkoh BCS spectra for very compact (and presumably relatively high-density) flares. No such effects were observed, leading to the conclusion that even for the most compact flares the electron density is less than 10^14 cm-3. Possible polarization effects (anomalous ratios of the intercombination x and y lines) were searched for in the Yohkoh data, but none has been found.
Ken Phillips, Jim Lemen, and Andrzej Fludra met in MSSL on 25th Nov to discuss various outstanding questions...
At present work is continuing with the tokamak and SMM spectra...
Some further atomic calculations will be carried out for the q, r etc collision rates using the Born approximation within the Cowan code.
Update 22-Aug-95
Submitted a paper to A & Ap.
Helium Like Sulphur X-ray Emission in Solar Flares and Laboratory Plasmas
L.K. Harra--Murnion^1, K.J.H. Phillips^2, J.R. Lemen^3, D.M. Zarro^4, C.J. Greer^5, V.J. Foster^5, R. Barnsley^6, I.H. Coffey^5, J. Dubau^7,
ABSTRACT
Theoretical X-ray spectra of He-like sulphur (Sxv) derived from the General Relativistic Atomic Structure Package, the Dirac R-matrix code and other calculations are compared to laboratory spectra obtained from the Alcator C tokamak and JET, and solar flare spectra obtained from the YOHKOH Bragg Crystal Spectrometer (BCS) and with the SMM Flat Crystal Spectrometer. The spectra depend on electron temperature and electron density for plasma densities greater than 10^14 cm^3. The fits of the derived synthetic spectra to the laboratory spectra at measured density and temperature are in fair agreement. Very good agreement can be achieved with the solar flare spectra, which are in general consistent with the Sxv low-density limit, by adjusting temperature. Thus, Sxv line spectra can be used to determine the temperatures of relatively weak flares for which diagnostics from higher-temperature ions are unavailable. Using the synthetic spectra, a search for density effects in YOHKOH BCS data at the time of compact flares was made. None was found, so that it can be deduced that for such flares the electron density is less than 10^14 cm^-3. Density estimates are made from emission measures and image sizes using YOHKOH Soft X-ray Telescope data. Research has been carried out with the results of laboratory spectra which indicate a variation of the I_x/I_y line intensity ratio across the tokamak minor radius. We have studied various flares which occur at different locations across the solar disk to determine if the same effect exists on the Sun.