Understanding Jupiter's polar vortex crystals - ref: 4114

Project Description

In the atmospheres of most solar-system planets, including Earth, polar vortices are isolated single cyclones centred over or near the poles. By contrast, Jupiter's polar vortices have an unprecedented structure, as recently discovered by NASA's Juno probe, having a single cyclone over each pole surrounded by several other cyclones in crystalline patterns [1].

These crystalline structures, and how they change in time [2], were not predicted prior to being observed, and the mechanisms explaining their formation and evolution remain unknown. One possible mechanism is that moist convection (due to latent heat release from water condensation) produces small vortices in the polar regions, with the cyclones then migrating polewards via the 'beta-drift' mechanism and merging [3].

But models including these processes find random fields of chaotically-moving vortices in Jupiter's polar regions, rather than the orderly vortex crystals that are observed [4, 5]. This project's aim is to determine how different processes contribute to transforming Jupiter's poles from a sea of chaotic vortices to the crystalline order of the observed polar vortices.

We propose to use several numerical models to study how order the interaction of atmospheric fluid dynamics and other physical processes can bring order to Jupiter's polar regions. The models to be used range from a simple shallow-water model through to a state-of-the-art General Circulation Model (GCM) configured for Jupiter. Each of these models has been built using the 'Isca' modelling framework, developed at Exeter [6].

The advantage of using Isca for this project is that different processes can be turned on and off (e.g. moist convection) to test the role each process plays. Guided by the interests of the successful student, experiments will be conducted with each of the models to understand how such crystalline arrangements of vortices can be formed, how they are sustained, and how they may change over the remaining length of the Juno mission.

[1] Adriani et al, Nature, 555, 2018, [2] Agle et al, https://go.nasa.gov/2sgvwCc, 2019, [3] Thomson and McIntyre, JAS 73, 2016, [4] O'Neill et al, Nature Geoscience 8, 2015, [5] Brueshaber et al, Icarus 323, 2019, [6] Thomson and Vallis, Atmosphere, 10(12), 803, 2019.