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

Journal Article · Sat Nov 01 04:00:00 EST 1980 · Astrophys. J.; (United States)

DOI:https://doi.org/10.1086/158434· OSTI ID:6562977

Feldman, U; Doschek, G A; Kreplin, R W; Mariska, J T

High-resolution x-ray spectra of class M flares have been recorded by four Bragg crystal spectrometers (SOLFLEX = solar flare x-rays) flown by NRL on an Air Force spacecraft. The wavelength ranges are 1.82 to 1.97 A, 2.98 to 3.07 A, 3.14 to 3.24 A, and 8.26 to 8.53 A. Electron temperatures are derived from dielectronic satellite-line-to-resonance-line ratios as a function of time for several typical flares. Temperatures near 20 x 10/sup 6/ K are found for many of the events during the rise time; however, cases also appear to be common where the rise time temperatures are no higher than approx.13 x 10/sup 6/ K. Rise and decay times, and electron temperatures for the M flares, are compared with their corresponding values derived for the larger class X events. For two of the M flares, blueshifted components to the resonance lines of Ca XIX and Fe XXV were observed that indicate motions along the line of sight of about 400 km s/sup -1/. These components existed during the rise phases of the events, and disappeared shortly after maximum flux was reached in the non-Doppler shifted components of the lines. As with the class X events, random nonthermal motions in M flare spectra are largest during the soft x-ray rise phase. A method proposed by Gabriel and Phillips for detecting possible nonthermal components to the electron Maxwellian distribution is discussed in light of our observations. The method is not sufficiently sensitive to give reliable results.

• Research Organization: Naval Research Lab., Washington, DC
• OSTI ID: 6562977
• Journal Information: Astrophys. J.; (United States), Journal Name: Astrophys. J.; (United States) Vol. 241:3; ISSN ASJOA
• Country of Publication: United States
• Language: English

Related Subjects

640104* -- Astrophysics & Cosmology-- Solar Phenomena
71 CLASSICAL AND QUANTUM MECHANICS
GENERAL PHYSICS
BOLTZMANN STATISTICS
CALCIUM IONS
CHARGED PARTICLES
ELECTROMAGNETIC RADIATION
ELECTRONS
ELEMENTARY PARTICLES
FERMIONS
IONIZING RADIATIONS
IONS
IRON IONS
LEPTONS
LINE WIDTHS
RADIATIONS
SOLAR ACTIVITY
SOLAR ELECTRONS
SOLAR FLARES
SOLAR PARTICLES
SOLAR RADIATION
SOLAR X-RAY BURSTS
SPECTRA
STELLAR RADIATION
X RADIATION
X-RAY SPECTRA