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Session 1 - Chromosphere, Corona, Flares.
Display session, Friday, June 27
Ballroom B, Chair: Charles Kankelborg

[1.56] The Variation of the Differential Emission Measure versus Temperature During the Decay Phase of Solar Flares

J. McTiernan (Space Sciences Lab, U.C. Berkeley)

We study the behavior of the decay phase of flares using data from the Yohkoh SXT, BCS and the GOES satellites. In previous work, we have noted the difference in the slopes of log(n) - log(T) plots for the SXT and GOES. We now add BCS data into the mix; instead of trying to fit the line profiles in the BCS channels directly we use the total line flux in each channel to find temperatures and emission measures. The loss of all information about the motion of the soft X-ray plasma is offset by tha fact that we can now use BCS in the same manner as the broad-band detectors, SXT and GOES, to obtain information about the Differential Emission Measure (DEM). We use parametrized model fits to the DEM, along with multi-temperature models, to estimate the dependence of the plasma cooling time as a function of temperature. From preliminary results, we see that the flare plasma is not isothermal, and it is often difficult to describe the DEM using any smoothly decreasing function; functions of temperature with multiple peaks are more useful. Using any kind of model, we find that higher temperature plasma peaks earlier and cools faster.

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