Waves and Turbulence: Their Cooperative Role in Structure Formation

Fluids and plasmas in a near dissipationless regime commonly exhibit well-defined, coherent structures. We observe these directly in weather patterns, in the zonal jets on Jupiter and the Great Red Spot, in sunspots and magnetic coronal loops, etc. In fact, observations of coherent structures are so widespread that we seldom question why. Such fluids and plasmas are very large order dynamical systems, and therefore appear to have ample freedom to explore near endless states or configurations. Why are so many of these structured — or why do these systems prefer to be in a structured state? In molecular dynamics, by contrast, despite the large numbers of degrees of freedom, structured states are extremely improbable. In this paper, we explore what makes fluids in particular favour structured states.