Basic observational characteristics of impulsive SXR brightenings Original Research Article

25 flares showing impulsive SXR brightenings have been investigated. The Yohkoh/SXT images have been used. The individual regions of the SXR response for each flare have been carefully localized. Some observational characteristics of them have been obtained. The results are presented in the form of histograms. For more comprehensive analysis HXR data from the Yohkoh/HXT has been incorporated. For several cases the velocity of plasma motions due to the chromospheric evaporation has been estimated directly from the SXR images. The obtained results will help to distinguish impulsive SXR brightenings from other effects and will be useful for theoretical modeling of the flare impulsive phase.