A study of opacity in SOHO-SUMER and SOHO-CDS spectral observations - III. The validity of the escape probability model

G.A. Fischbacher, S.D. Loch, H.P. Summers

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The assumptions underpinning escape probability and absorption factor methods for describing spectral emission from optically thick plasmas, are addressed to test the range of validity of the associated expressions and to develop them for use within non-stratified atmospheres which include plasma flow and line blending. It is found that for moderate optical depths ( ~10) the escape probability is an effective tool for accurately describing the effect of opacity on emergent spectral line intensities. Furthermore it is found that the expressions may be used to extract optical depths directly from observational data independently of preconceived atmosphere model ideas. The analysis enables the detection of unresolved spicule-like structures at the solar limb.
Original languageEnglish
Pages (from-to)295-313
Number of pages18
JournalAstronomy and Astrophysics
Issue number1
Publication statusPublished - Jul 2002


  • atomic data
  • atomic processes
  • sun
  • atmosphere
  • UV radiation
  • plasma

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