Abstract

A fascinating and surprising phenomenon that can occur in fluid and plasma turbulence is the spontaneous formation of arrays of layers in which material properties such as density adopt a so-called “staircase” structure. The most striking examples are potential vorticity staircases in planetary atmospheres, and thermohaline staircases in the oceans. Theoretical considerations suggest that layering also plays an important role in stellar interiors (particularly through various double-diffusive processes) and in fusion confinement devices (the so-called E x B staircase). Understanding the phenomenon of layering is, therefore, not only of intrinsic scientific interest (e.g., is there a common thread to layering in these very different contexts?), but is also crucial for an accurate description of turbulent transport in, for example, models of large-scale ocean flow, the evolution of stellar interiors and confinement in tokamaks.