High Resolution Solar Flare X-Ray Spectra: The Temporal Behavior of Electron Density, Temperature, and Emission Measure for Two Class M Flares.
AEROSPACE CORP EL SEGUNDO CA SPACE SCIENCES LAB
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High resolution soft x-ray flare spectra recorded by Naval Research Laboratory NRL and Aerospace Corporation Bragg crystal spectrometers flown on an orbiting spacecraft P78-1 are combined and analyzed. The instruments were launched on 1979 February 24 by the U.S. Air Force and the data discussed in this paper cover the wavelength ranges, 1.82-1.97 A, 3.14-3.24 A, and 18.4-23.0 A. The NRL experiment SOLFLEX covers the two short wavelength ranges highly ionized Fe and Ca lines and the Aerospace experiment SOLEX covers the 18.4-23.0 A range, which includes the Ly-alpha O VIII line and the resonance intercombination, and forbidden lines of O VII. We analyze the spectra of two flares which occurred on 1980 April 8 and May 9. Temporal coverage is fairly complete for both flares, including the rise and decay phases. Measurements of electron density Ne with rather high time resolution about 1 minute have been obtained throughout most of the lifetimes of the two flares. These measurements were obtained from the O VII lines and pertain to flare plasma at temperatures near 2,000,000 K. Peak density seems to occur slightly before the times of peak X-ray flux in the resonance lines of Fe XXV, Ca XIX, and O VII, and for both flares the peak density is about 10 to the 12th powercc. Electron temperature Te as a function of time is determined from the Fe and Ca spectra. Peak temperature for both flares is about 18,000,000 K. Differential emission measures and volume emission measures are determined for the low O VII and high temperature Fe, Ca plasma.