PROPERTIES OF SOLAR FLARE PLASMAS DERIVED FROM SOFT X-RAY LINE EMISSION

A new observational property of soft X-ray line fluxes observed during the decay phase of solar flares is described and a new technique is presented for determining the plasma temperature and emission measure as functions of time based on this property. Results of this technique indicate the need for continuous heating or an intermediate energy storage mechanism during the flare. Fluid turbulence is examined as a possible intermediate energy storage mechanism.;The proposed explanation for the rate changes was used to develop a technique for estimating the temperature and emission measure as a function of time during the gradual phase of solar flares. Eight flares were modeled with this technique and the model fits were repeated for each flare using five different sets of published line emissivity calculations.;Estimates were made of various plasma parameters based on the model results during the decay of the 1980 November 5 flare. The mass was found to remain constant as the volume expanded, and the change in thermal energy was insufficient to account for the predicted total radiative losses, indicating the need for additional heating during the decay phase of this flare.;Turbulence is proposed as a method for converting the energy observed as mass motions during the impulsive phase into thermal energy and the subsequent thermal radiation observed during the gradual phase of solar flares. The general properties of steady state, homogeneous fluid turbulence and of turbulent decay are reviewed, and the time dependent behavior is compared with the velocities and energies observed by SMM's BCS during the 1980 November 5 flare.;The soft X-ray line fluxes observed by SMM's FCS during the gradual phase of the 1980 November 5 flare did not decay at a constant rate. The line flux decay rate changed abruptly, with the line fluxes falling more rapidly 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.