The $E \times B$ staircase as the self-organization in the tokamak avalanche plasma

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. Various models have been suggested to understand this globally self-organized state of transport barriers and its relation with the avalanche transport. While intensive simulation studies have been conducted to advance the understanding, the experimental researches have been mostly limited to the demonstration of their existence. In this work, detail characteristics of both the avalanche transport and the $E \times B$ staircase in KSTAR plasmas are analyzed. The avalanche transport is found to have strong influences on the formation and statistics of the $E \times B$ staircase. In addition, a perspective to consider the $E \times B$ staircase as the self-organization near an non-equilibrium critical state is discussed to understand its dynamics and statistics and the relation with the stationary internal transport barrier.