A „typical” impulsive SXR brightening: 1. Lasts about 0.5-1min. 2. Has symmetrical time profile. 3. The diameter is about 2-8 SXT pixels. 4. Temperature below 10 MK and electron density below 10 11 cm -3. 5. Relative brightness below 0.1. 6. Lasts several times longer than HXR burst. 7. Shows a delay in comparision with the HXR burst. 8. Delay has Poisson distribution (τ = 35 s).
CONCLUSIONS 1.The described characteristics should help to distinguish the impulsive SXR brightenings from other morphological features and should help in the modelling of the impulsive phase. 2.A generally good spatial and temporal correlation between impulsive SXR brightenings and HXR bursts strongly suggests the same origin : non-thermal electron beams. 3.The strong correlation between the SXR and HXR response can be considered to be a proof that impulsive SXR brightenings are directly responsible for the Neupert effect. 4.A steeper energy spectrum of HXR photons causes a higher relative productivity of SXRs. 5.There is a correlation between the energies : the total, time-integrated energy deposited by non-thermal electrons and the maximum thermal energy contained in the plasma heated by those particles.