Simulating Flaring Events in Complex Active Regions Driven by Observed   Magnetograms
  We interpret solar flares as events originating from active regions that have reached the Self Organized Critical state, by using a refined Cellular Automaton model with initial conditions derived from observations. Aims: We investigate whether the system, with its imposed physical elements,reaches a Self Organized Critical state and whether well-known statistical properties of flares, such as scaling laws observed in the distribution functions of characteristic parameters, are reproduced after this state has been reached. Results: Our results show that Self Organized Criticality is indeed reached when applying specific loading and relaxation rules. Power law indices obtained from the distribution functions of the modeled flaring events are in good agreement with observations. Single power laws (peak and total flare energy) as well as power laws with exponential cutoff and double power laws (flare duration) are obtained. The results are also compared with observational X-ray data from GOES satellite for our active-region sample. Conclusions: We conclude that well-known statistical properties of flares are reproduced after the system has reached Self Organized Criticality. A significant enhancement of our refined Cellular Automaton model is that it commences the simulation from observed vector magnetograms, thus facilitating energy calculation in physical units. The model described in this study remains consistent with fundamental physical requirements, and imposes physically meaningful driving and redistribution rules. 
M. Dimitropoulou, H. Isliker, L. Vlahos, M.K. Georgoulis
astro-ph.SR