Time-energy correlations in solar flare occurrence

Context. The existence of time-energy correlations in flare occurrence is still an open and much debated problem. Aims. This study addresses the question whether statistically significant correlations are present between energies of successive flares as well as energies and waiting times. Methods. We analyze the GOES catalog with a statistical approach based on the comparison of the real catalog with a reshuffled one where energies are decorrelated. This analysis reduces the effect of background activity and is able to reveal the role of obscuration. Results. We show the existence of non-trivial correlations between waiting times and energies, as well as between energies of subsequent flares. More precisely, we find that flares close in time tend to have the second event with large energy. Moreover, after large flares the flaring rate significantly increases, together with the probability of other large flares. Conclusions. Results suggest that correlations between energies and waiting times are a physical property and not an effect of obscuration. These findings could give important information on the mechanisms for energy storage and release in the solar corona.