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High-resolution X-ray spectra of solar flares. III - General spectral properties of X1-X5 type flaresHigh-resolution X-ray spectra of six class X1-X5 solar flares are discussed. The spectra were recorded by spaceborne Bragg crystal spectrometers in the ranges 1.82-1.97, 2.98-3.07 and 3.14-3.24 A. Electron temperatures derived from dielectronic satellite line to resonance line ratios for Fe XXV and Ca XIX are found to remain fairly constant around 22,000,000 and 16,000,000 K respectively during the rise phase of the flares, then decrease by approximately 6,000,000 K during the decay phase. Nonthermal motions derived from line widths for the April 27, 1979 event are found to be greatest during the rise phase (approximately 130 km/sec) and decrease to about 60 km/sec during decay. Volume emission measures for Fe XXV, Ca XIX and Ca XX are derived from photon fluxes as a function of temperature, and examination of the intensity behavior of the Fe K alpha emission as a function of time indicates that it is a result of fluorescence. Differences between the present and previous observations of temperature variation are discussed, and it is concluded that the flare plasmas are close to ionization equilibrium for the flares investigated.
Document ID
19800066225
Acquisition Source
Legacy CDMS
Document Type
Reprint (Version printed in journal)
External Source(s)
Authors
Doschek, G. A.
(Hulburt (E. O.) Center for Space Research Washington, DC, United States)
Feldman, U.
(Hulburt (E. O.) Center for Space Research Washington, DC, United States)
Kreplin, R. W.
(U.S. Navy, E. O. Hulburt Center for Space Research, Washington D.C., United States)
Cohen, L.
(NASA Goddard Space Flight Center Laboratory for Solar Physics and Astrophysics, Greenbelt, Md., United States)
Date Acquired
August 10, 2013
Publication Date
July 15, 1980
Publication Information
Publication: Astrophysical Journal
Subject Category
Solar Physics
Accession Number
80A50395
Distribution Limits
Public
Copyright
Other

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