A mechanism for equatorial jet formation on ice giants

The equatorial jets observed on the Jovian planets - Jupiter, Saturn, Uranus, and Neptune - exhibit extreme equatorial zonal flow patterns, manifesting as either strongly prograde (in the gas giants) or strongly retrograde (in the ice giants). Existing theories have often treated gas giants and ice giants separately, primarily focusing on the differences between deep and shallow dynamics. However, recent gravity measurements suggest that the convective envelope of Jupiter may be similar to those of the ice giants, challenging the traditional distinctions between these planet types.We present results from a numerical simulation that introduces a mechanism capable of explaining the equatorial jets on the ice giants in a manner analogous to those on the gas giants. In these simulations, as shown theoretically by Busse et al., the convective dynamics and planetary rotation drive the formation of tilted convection columns. These columns, extending cylindrically from the deep interior to the outer atmospheric layers, play a crucial role in shaping the zonal wind patterns. In this study, the tilting of the convection columns introduces asymmetries in momentum transport, leading to a bifurcation of the flow into either superrotation (prograde jets) or subrotation (retrograde jets).Through a detailed analysis of the convection-driven columnar structures, we demonstrate that the equatorial wave properties and the leading-order momentum balance share remarkable similarities between the two types of solutions. Our findings comprehensively explain the potential for both superrotation and subrotation solutions under constant physical conditions, thereby potentially explaining the diverse zonal wind patterns observed on the Jovian planets and providing a deeper understanding of the mechanisms driving equatorial jet formation.