Waiting time statistics in solar flares

Solar fares activity is investigated by looking at the statistics of the wa iting times between hard X-ray bursts. It is found that the distribution ha s a power-law tail which indicates the existence of nontrivial dynamics wit h long-range correlations. A shell model for MHD turbulence is capable to r eproduce the power-law distribution through an identification of the interm ittent bursts of dissipation with solar flares. This result suggests that t he nonlinear dynamics could play a role more relevant than the particular t opology associated with the field configuration. Comparisons with results f rom models based on self-organized criticality are made. (C) 2000 Elsevier Science B.V. All rights reserved.