Layering in Atmospheres, Oceans and Plasmas

Coordinators: Patrick H. Diamond, Pascale Garaud, David W. Hughes, and Bruce Sutherland

Scientific Advisors: Mary-Louise Timmermans and Bill Young

This program will be held online. Those interested should apply using the link in the sidebar. Please ignore the application deadline.

Fluid and plasma turbulence often manifests the spontaneous formation of ‘staircases’ or layered structures – arrays of finite homogenized domains separated by sharp gradients that act as transport barriers. This is surprising, because normally one expects turbulent mixing to cause homogenization. Across a wide range of physical systems layering exerts a critical control on dynamics and transport:

  • For staircases in density stratified fluids, turbulence forms layers by still poorly understood ‘self-sharpening effects’ in density mixing. This is of great importance to a wide range of atmosphere, ocean, and engineering applications.
  • For potential vorticity (PV) staircases in rotating geophysical fluid systems, sequences of PV jumps form that are associated with sharp jets and act as barriers to material transport.
  • Staircases in magnetized plasmas constitute an important new type of secondary pattern. They resemble a lattice of internal transport barriers and their scales define the effective mixing or transport scale of the system. The latter is a major issue in fusion science.
  • For layering in doubly diffusive convection that occurs in oceans, planetary atmospheres, and stellar interiors, the mechanisms leading to long-lived density staircases remain unsettled, especially in light of inconsistencies between simulations and observations.

This program will foster interdisciplinary interaction among plasma physicists, oceanographers, geophysical and astrophysical fluid dynamicists, soft-condensed-matter physicists and applied mathematicians—all of whom confront problems in layering. The aims are cross-disciplinary fertilization, nucleation of new collaborations, and progress toward a collective understanding of what physics is fundamental to the occurrence of layering.