  Numerous land and space-based observations have established that Saturn has a
persistent hexagonal flow pattern near its north pole. While observations
abound, the physics behind its formation is still uncertain. Although several
phenomenological models have been able to reproduce this feature, a
self-consistent model for how such a large-scale polygonal jet forms in the
highly turbulent atmosphere of Saturn is lacking. Here we present a 3D
fully-nonlinear anelastic simulation of deep thermal convection in the outer
layers of gas giant planets which spontaneously generates giant polar cyclones,
fierce alternating zonal flows, and a high latitude eastward jet with a
polygonal pattern. The analysis of the simulation suggests that self-organized
turbulence in the form of giant vortices pinches the eastward jet, forming
polygonal shapes. We argue that a similar mechanism is responsible for exciting
Saturn's hexagonal flow pattern.
