E. Oshea et al., EUV EMISSION-LINES OF O-IV OBSERVED IN SOLAR SPECTRA BY THE S-055 INSTRUMENT ON SKYLAB, Astronomy and astrophysics, 306(2), 1996, pp. 621-624
Recent calculations of electron and proton impact excitation rates in
O IV are used to derive the intensity ratios of lines in the similar t
o 340-1350 Angstrom wavelength range as a function of electron tempera
ture (T-e) and density (N-e). These results are presented in the form
of ratio-ratio diagrams, which should in principle allow both N-e and
T-e to be deduced for the O IV line emitting region of a plasma. Elect
ron temperatures derived from ratio-ratio diagrams involving the 790 A
ngstrom/554 Angstrom ratio, in conjunction with observational data for
several solar features obtained with the Harvard S-055 spectrometer o
n board Skylab, are found to be in reasonable agreement with the value
of T-e expected from ionization equilibrium calculations. This provid
es some support for the theoretical diagnostics presented in this pape
r, and hence the atomic data used in their derivation. However other t
emperature and density sensitive ratios involving the O IV multiplets
at 609 Angstrom, 625 Angstrom and 787 Angstrom could not be used to de
rive plasma parameters from the ratio-ratio diagrams, due to blending
with lines of Mg X and S V.