Internal Transport Barriers in Fluids and Plasmas

Turbulent flow in neutral fluids and fusion plasmas is known to have many commonalities, one example being the application of energy and enstrophy cascades. In this review, we discuss a novel cyclic process which may also be common to both fluids and plasmas: This includes exact coherent states (or magnetic islands), Reynolds stress-driven (zonal) flows and internal interface layers (or internal transport barriers). We briefly review the current understanding of internal interface layers in fluids and discuss open questions and possible research directions to pursue. The main objective of our review is to create awareness of the shared mechanism to motivate further interdisciplinary research in this field, both by the fluid mechanics and plasma physics communities.