Abstract

The self-organization is one of the most interesting phenomena in the non-equilibrium complex system, generating ordered structures of various size and duration. The physical mechanism and characteristics of the self-organization phenomena are closely related with the underlying transport mechanism and characteristics. In tokamak plasmas, globally self-organized mini transport barriers, the $E \times B$ staircase, are observed in the particular transport regime where non-diffusive flux propagation events, the avalanche, are prevalent. In this talk, detail characteristics of both the avalanche transport and the $E \times B$ staircase in KSTAR plasmas are analyzed to understand their relation. The avalanche transport is found to have strong influences on the formation and the width distribution of the $E \times B$ staircase, while the $E \times B$ staircase confines the avalanche propagation within its width until it is dissipated. A perspective to consider the $E \times B$ staircase as the self-organization near an non-equilibrium critical state provides understanding of not only its dynamics and statistics but also the relation with the stationary internal transport barrier. In some sense, the $E \times B$ staircase and the avalanche can be thought as two faces of the same thing. They both efficiently remove an excess energy from the system so that it can reach a stationary state. Which process will be chosen may depend on an instant status of environment.