25 Years of SelfOrganized Criticality: Solar and Astrophysics
Abstract
Shortly after the seminal paper "SelfOrganized Criticality: An explanation of 1/ f noise" by Bak et al. (1987), the idea has been applied to solar physics, in "Avalanches and the Distribution of Solar Flares" by Lu and Hamilton (1991). In the following years, an inspiring crossfertilization from complexity theory to solar and astrophysics took place, where the SOC concept was initially applied to solar flares, stellar flares, and magnetospheric substorms, and later extended to the radiation belt, the heliosphere, lunar craters, the asteroid belt, the Saturn ring, pulsar glitches, soft Xray repeaters, blazars, blackhole objects, cosmic rays, and boson clouds. The application of SOC concepts has been performed by numerical cellular automaton simulations, by analytical calculations of statistical (powerlawlike) distributions based on physical scaling laws, and by observational tests of theoretically predicted size distributions and waiting time distributions. Attempts have been undertaken to import physical models into the numerical SOC toy models, such as the discretization of magnetohydrodynamics (MHD) processes. The novel applications stimulated also vigorous debates about the discrimination between SOC models, SOClike, and nonSOC processes, such as phase transitions, turbulence, randomwalk diffusion, percolation, branching processes, network theory, chaos theory, fractality, multiscale, and other complexity phenomena. We review SOC studies from the last 25 years and highlight new trends, open questions, and future challenges, as discussed during two recent ISSI workshops on this theme.
 Publication:

Space Science Reviews
 Pub Date:
 January 2016
 DOI:
 10.1007/s1121401400546
 arXiv:
 arXiv:1403.6528
 Bibcode:
 2016SSRv..198...47A
 Keywords:

 Instabilities;
 Methods: statistical;
 Sun: flare;
 Stars: flare;
 Planets and satellites: rings;
 Cosmic rays;
 Astrophysics  Instrumentation and Methods for Astrophysics;
 Astrophysics  Solar and Stellar Astrophysics
 EPrint:
 139 pages, 28 figures, Review based on ISSI workshops "SelfOrganized Criticality and Turbulence" (2012, 2013, Bern, Switzerland)