Self‐Organized Hexagon‐Shaped Jets in Rotating Fluid Experiments

Self‐organization of planetary turbulence in persistent and geometrically well‐defined flow features, has been attracting, recently, great scientific interest, thanks also to the spectacular images of Saturn's hexagon provided by the Voyager and Cassini missions. These flow patterns can be replicated in laboratory experiments with shallow rotating fluids, provided some characteristic non‐dimensional parameters are suitably set up. In particular, we consider here prograde and retrograde (with respect to the rotation of the tank) hexagonal‐shaped jets. Both Eulerian and Lagrangian data, directly reconstructed from the experiments, were analyzed and discussed. Our results are consistent with the conjecture that barotropic instability plays a key role in the genesis and maintenance of the hexagonal shape. We also show that the cross‐analysis of experimental results and kinematic simulations on a simplified six‐node meandering jet model allows, in principle, to formulate a scenario about the Lagrangian dispersion properties of the hexagon on Saturn in relation to its spatial and temporal characteristic scales.