Dynamical constraints on the vertical structure of Jupiter's polar cyclones

TL;DR

This paper uses a 2D quasi-geostrophic model to link the observed westward drift of Jupiter's polar cyclones to their vertical structure, providing constraints for interpreting future Juno measurements.

Contribution

It introduces a novel approach to constrain the vertical extent of Jupiter's polar cyclones using their long-term drift behavior and a 2D model.

Findings

Shallower cyclones drift more slowly due to vortex stretching.

The deformation radius constrains the cyclones' vertical structure.

Results inform interpretation of upcoming Juno measurements.

Abstract

Jupiter's poles feature striking polygons of cyclones that drift westward over time, a motion governed by beta-drift (vortex motion caused by the latitudinal variation of the Coriolis force). This study investigates how beta-drift and the resulting westward motion depend on the depth of these cyclones. Counterintuitively, shallower cyclones drift more slowly, a consequence of stronger vortex stretching. By employing a 2D quasi-geostrophic model of Jupiter's polar regions, we constrain the cyclones' deformation radius, a key parameter that serves as a proxy for their vertical extent, required to replicate the observed westward drift. We then explore possible vertical structures and the static stability of the poles by solving the eigenvalue problem that links the 2D model to a 3D framework, matching the constrained deformation radius. These findings provide a foundation for interpreting upcoming Juno microwave measurements of Jupiter's north pole, offering insights into the static stability and vertical structure of the polar cyclones. Thus, by leveraging long-term motion as a novel constraint on vertical dynamics, this work sets the stage for advancing our understanding of the formation and evolution of Jupiter's enigmatic polar cyclones.