Astronomy and Astrophysics – Astrophysics
Scientific paper
Aug 1994
adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=1994apj...431..888d&link_type=abstract
The Astrophysical Journal, vol. 431, no. 2, pt. 1, p. 888-900
Astronomy and Astrophysics
Astrophysics
17
Emission Spectra, Gamma Rays, Line Spectra, Particle Acceleration, Solar Flares, X Ray Spectra, Astronomical Models, Cosmology, Plasma Heating, Spectrum Analysis, Stellar Evolution, X Ray Imagery
Scientific paper
We discuss X-ray spectra and soft X-ray images of an M1.9 flare that occurred on 1991 November 9 near 03.2 UT. These data were obtained with instrumentation on the Japanese Yohkoh spacecraft. They cover the entire rise phase and peak flare emission, and the beginning of the decay phase. We determine the dynamics, temperature, and emission measure of the flare as inferred from the X-ray line profiles of resonance lines of Fe XXV, Ca XIX, and S XV. We discuss the morphology of the flare as inferred from the soft X-ray images. The November 9 flare is atypical in that a stronger than usual blueshifted emission component (relative to the stationary component) is observed for the resonance lines at flare onset. We discuss several methods for deconvolving the blueshifted component from the stationary component. The X-ray line profiles are consistent with predictions of numerical simulations of chromospheric evaporation. The X-ray images reveal a flare with a complicated loop geometry that is not fully understood. Many of the features in the images are moving upwards at speeds ranging from a few km/s to about 800 km/s. The blueshifted emission begins near the onset of hard X-ray emission, implying that particle acceleration and upflowing plasma have a common energy source.
Bentley Robert D.
Brown Charles Max
Culhane Leonard J.
Doschek George A.
Lang Jaclyn
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