Analysis of differential emission measure evolution for selected SEP and non-SEP associated flares based on hard and soft X-ray observations

We present prompt results of analysis of differential emission measure distributions (DEM) for solar flares. The DEM describes the distribution of emitting plasma with temperature. For calculations of the DEM shape we use Withbroe - Sylwester (WS) multiplicative iterative algorithm. Our input data set consists of total flare fluxes as measured by the Yohkoh Soft X-ray Telescope (SXT) in most of available filters, the Hard X-ray Telescope data (HXT), the Bragg Crystal Spectrometer (BCS) line fluxes and GOES X-ray fluency as measured in 0.5 - 4Angstrom and 1- 8 Angstrom bands. Reconstruction of DEM shape from observed X-ray fluxes constitute uneasy ill-defined inverse problem. Therefore, before applying the algorithm to real data we performed numerous tests of the inversion method using several synthetic DEM distributions. This has been done in order to better understand how to interpret the DEM as obtained from real measurements and understand limitations of the inversion procedure. In our tests, we have used a number of typical DEM distribution shapes (cf. Figure 2). The overall stability of the WS reconstruction procedure led us to investigate DEM shapes for particular flare events selected. We have chosen to look for possible differences in DEM shape and behavior for flare events which have been associated and not associated with the (following) solar energetic particle (SEP) occurrence.