From Gas to Ice Giants: A Unified Mechanism for Equatorial Jets

The equatorial jets dominating the dynamics of the Jovian planets  exhibit two distinct types of zonal flows: strongly eastward (superrotation) and strongly westward (subrotation). Existing theories propose different mechanisms for these patterns on gas giants and ice giants, but no single mechanism has successfully explained both. However, the planetary parameters of the four Solar System giant planets suggest that a fundamentally different mechanism is unlikely. In this study, we demonstrate that a convection-driven columnar structure can explain the equatorial jets on all four Jovian planets, framing the problem as a bifurcation phenomenon. Consequently, both superrotation and subrotation emerge as stable branches of the same mechanistic solution. Our analysis of these solutions uncovers similarities in the properties of equatorial waves and the leading-order momentum balance. This study reveals that the underlying dynamics of equatorial jet formation are more universally applicable across the Jovian planets than previously thought, providing a unified explanation for their two distinct zonal wind patterns.