Observable features of avalanching systems

Avalanching systems are very ubiquitous in nature. They are often related to self-organized criticality (SOC), although the avalanching feature is more general. SOC has been proposed as a universal mechanism for the behaviour of a wide class of statistical systems and phenomena (magnetic substorms, solar flares, earthquakes, rainfall, forest fires, etc.). Research in this area mainly concentrates on what is considered to be the basic features of avalanching systems and SOC in particular: statistics of avalanches, self-similarity, and large correlation length. Despite substantial efforts, no physical system with firmly established SOC behaviour has been observed: existence of a critical state without tuning parameter in avalanching observed avalanching systems has not been proven. Universal features of avalanching models have been extensively studied. Nevertheless, applicability of this studies to real physical systems in still under question. This is partly because of the lack of studies of what and how should be measured in real systems to identify manifestations of SOC and to relate the internal (not directly observable) processes to measurable parameters. The objective of the proposed research is to properly establish what physical variables (output) should be studied in real physical systems (like magnetosphere or earthquakes) in order to make firm conclusions about presence or absence of SOC and study the relation between the driving (input) and microprocesses in the avalanching systems and the output. As a result of the hopefully successful research we will have appropriate tools to distinguish SOC systems from non-SOC ones and will be able to conclude about the microprocesses in avalanching systems from observations of some macroscopic variables.