The waiting-time distribution of solar flare hard X-ray bursts

A waiting-time distribution is constructed for 8 yr of solar flare hard X-r ay bursts observed by the ICE/ISEE 3 spacecraft. The observed distribution is compared with a simulated waiting-time distribution produced by a time-d ependent Poisson process constructed using rates estimated from the observa tions. The observed distribution shows an overabundance of short waiting ti mes (10 s-10 minutes) in comparison with the simulation. This result implie s that the hard X-ray bursts are not independent events. The implications o f this result for the existence of sympathetic flaring and to models of har e statistics are discussed, and the result is compared with previous determ inations of waiting-time distributions for solar hard X-ray events.