Vortex Street Dynamics: The Selection Mechanism for the Areas and Locations of Jupiter’s Vortices

Abstract

Abstract With the exception of the Great Red Spot, Jupiter’s long-lived vortices are not isolated, but occur in east–west rows. Each row is centered about a westward-going jet stream with anticyclones on the poleward side and cyclones on the equatorial. Vortices are staggered so that like-signed vortices are never longitudinally adjacent. These double rows of vortices, called here Jovian vortex streets (JVSs) are robust. Calculations with no forcing and no dissipation (i.e., Hamiltonian dynamics) allow a continuum of JVS solutions, so they cannot be used to determine the physics that selects the observed values of the areas, circulations, and locations of Jupiter’s vortices. Constraints imposed by stability put few bounds on these values. When small amounts of dissipation and forcing are added to the governing equations, there is no longer a continuum of solutions; an initial JVS that was a solution of the Hamiltonian equations is now out of equilibrium and evolves to an attractor. For fixed forcing, all initial JVS evolve to the same attractor, so that the area of the vortices in the late-time JVS is selected uniquely as is the separation width in latitude between the row of cyclones and row of anticyclones. The separation width of the attracting JVS is nearly independent of the forcing, but the areas of the vortices in the attracting JVS depend strongly on the strength of the forcing, which is a measure of the ambient Jovian turbulence. Results are compared with observations.