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-ray bursts observed by the ICE/ISEE 3 spacecraft. The observed distribution is compared with a simulated waiting-time distribution produced by a time-dependent Poisson process constructed using rates estimated from the observations. The observed distribution shows an overabundance of short waiting times (10 s-10 minutes) in comparison with the simulation. This result implies that the hard X-ray bursts are not independent events. The implications of this result for the existence of sympathetic flaring and to models of hare statistics are discussed, and the result is compared with previous determinations of waiting-time distributions for solar hard X-ray events.