Flarelike brightenings of active region loops observed with SUMER

Coronal loops on the east limb of the Sun were observed by SUMER on SOHO for several days. Small flare-like brightenings are detected very frequently in the hot flare line Fe~{\small XIX}. We find that the relatively intense events are in good coincidence with the transient brightenings seen by Yohkoh/SXT. A statistical analysis shows that these brightenings have durations of 5-84 min and extensions along the slit of 2-67 Mm. The integrated energy observed in Fe~{\small XIX} for each event is in the range of $3\times {10}^{18}-5\times {10}^{23}$ ergs, and the estimated thermal energy ranges from ${10}^{26}-{10}^{29}$ ergs. Application of the statistical method proposed by Parnell & Jupp (2000) yields a value of 1.5 to 1.8 for the index of a power law relation between the frequency of the events and the radiated energy in Fe~{\small XIX}, and a value of 1.7 to 1.8 for the index of the frequency distribution of the thermal energy in the energy range $>{10}^{27}$ ergs. We examine the possibility that these small brightenings give a big contribution to heating of the active region corona.