High-resolution X-ray spectra of solar flares. IV - General spectral properties of M type flares

Abstract

view Abstract Citations (119) References (11) Co-Reads Similar Papers Volume Content Graphics Metrics Export Citation NASA/ADS High-resolution X-ray spectra of solar flares. IV - General spectral properties of M type flares Feldman, U. ; Doschek, G. A. ; Kreplin, R. W. ; Mariska, J. T. Abstract The spectral characteristics in selected narrow regions of the X-ray spectrum of class M solar flares are analyzed. High-resolution spectra in the ranges 1.82-1.97, 2.98-3.07, 3.14-3.24 and 8.26-8.53 A, which contain lines important for the determination of electron temperature and departure from ionization equilibrium, were recorded by spaceborne Bragg crystal spectrometers. Temperatures of up to 20,000,000 K are obtained from line ratios during flare rise phases in M as well as X flares, while in the decay phase the calcium temperature can be as low as 8,000,000 K, which is significantly lower than in X flares. Large nonthermal motions (on the order of 130 km/sec at most) are also observed in M as well as X flares, which are largest during the soft X-ray rise phase. Finally, it is shown that the method proposed by Gabriel and Phillips (1979) for detecting departures of electrons from Maxwellian velocity distributions is not sufficiently sensitive to give reliable results for the present data. Publication: The Astrophysical Journal Pub Date: November 1980 DOI: 10.1086/158434 Bibcode: 1980ApJ...241.1175F Keywords: Solar Flares; Solar Spectra; Solar X-Rays; X Ray Spectra; Electron Energy; High Resolution; Spectral Line Width; Solar Physics full text sources ADS | Related Materials (8) Part 1: 1979ApJ...233L.157D Part 2: 1980ApJ...238..365F Part 3: 1980ApJ...239..725D Part 5: 1981ApJ...245..315D Part 6: 1982ApJ...260..885F Part 7: 1985ApJ...292..309K Part 8: 1986ApJ...306..327K Part 9: 1989ApJ...345.1079D