paper

A Statistical Fractal-Diffusive Avalanche Model of a Slowly-Driven Self-Organized Criticality System

arXiv:1112.4859 · doi:10.1051/0004-6361/201118237

Abstract

We develop a statistical analytical model that predicts the occurrence frequency distributions and parameter correlations of avalanches in nonlinear dissipative systems in the state of a slowly-driven self-organized criticality (SOC) system. This model, called the fractal-diffusive SOC model, is based on the following four assumptions: (i) The avalanche size grows as a diffusive random walk with time , following ; (ii) The instantaneous energy dissipation rate occupies a fractal volume with dimension , which predicts the relationships , for the peak energy dissipation rate, and for the total dissipated energy; (iii) The mean fractal dimension of avalanches in Euclidean space is ; and (iv) The occurrence frequency distributions based on spatially uniform probabilities in a SOC system are given by , which predicts powerlaw distributions for all parameters, with the slopes , , , and . We test the predicted fractal dimensions, occurrence frequency distributions, and correlations with numerical simulations of cellular automaton models in three dimensions and find satisfactory agreement within . One profound prediction of this universal SOC model is that the energy distribution has a powerlaw slope in the range of , and the peak energy distribution has a slope of (for any fractal dimension in Euclidean space S=3), and thus predicts that the bulk energy is always contained in the largest events, which rules out significant nanoflare heating in the case of solar flares.

9 Figures, 1 movie available at authors website, http://www.lmsal.com/~aschwand/eprints/cellular_automaton_movie.jpeg

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