New method for determining temperature and emission measure during solar flares from light curves of soft X-ray line fluxes
I describe a new property of soft X-ray line fluxes observed during the decay phase of solar flares and a technique for using this property to determine the plasma temperature and emission measure as functions of time. The soft X-ray line fluxes analyzed in this paper were observed during the decay phase of the 1980 November 5 flare by the X-Ray Polychromator (XRP) instrument on board the Solar Maximum Mission (SMM). The resonance, intercombination, and forbidden lines of Ne IX, Mg XI, Si XIII, S XV, Ca XIX, and Fe XXV, as well as the Lyman-..cap alpha.. line of O VIII and the resonance lines of Fe XIX, were observed. The rates at which the observed line fluxes decayed were not constant. For all but the highest temperature lines observed, the rate changed abruptly, causing the fluxes to fall at a more rapid rate later in the flare decay. These changes occurred at earlier times for lines formed at higher temperatures. This behavior is proposed to be due to the decreasing temperature of the flare plasma tracking the rise and subsequent fall of each line emissivity function. This explanation is used to empirically model the observed light curves and to estimate the temperature and the change in emission measure of the plasma as a function of time during the decay phase. Estimates are made of various plasma parameters based on the model results.
- Research Organization:
- Joint Institute for Laboratory Astrophysics, University of Colorado and National Bureau of Standards; and Department of Astrophysical, Planetary and Atmospheric Sciences, University of Colorado
- OSTI ID:
- 5258689
- Journal Information:
- Astrophys. J.; (United States), Vol. 293:2
- Country of Publication:
- United States
- Language:
- English
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Related Subjects
GENERAL PHYSICS
SOLAR FLARES
SOFT X RADIATION
EMISSION SPECTRA
PLASMA
RADIATION FLUX
SOLAR RADIATION
STAR MODELS
ELECTROMAGNETIC RADIATION
IONIZING RADIATIONS
MATHEMATICAL MODELS
RADIATIONS
SOLAR ACTIVITY
SPECTRA
STELLAR RADIATION
X RADIATION
640104* - Astrophysics & Cosmology- Solar Phenomena