Emergence and equilibration of zonal winds on giant planets: a wave-mean flow interaction approach

The Vortex Dynamics group in the School of Mathematics and Statistics at the University of St Andrews is looking for applicants for a PhD studentship for a start in September 2025. The successful applicant will be supervised by Dr Daphné Lemasquerier and work on a recently-awarded UKRI Future Leaders Fellowship (FLF) project entitled “Fluid Dynamics of Deep Interiors in the Outer Solar System”. The studentship is fully funded (fees, plus stipend of approx. £19,237), and open to home and international students.

The deep atmospheric dynamics of gas giants is a fascinating example of how a chaotic flow can self-organise at large scale. In particular, Jupiter’s bands result from intense east-west winds, so-called “zonal jets”, whose origin, stability and three-dimensional structure are still puzzling the scientific community. Recent measurements performed by the Juno spacecraft led to significant advances, but direct observations are limited to the cloud layer which covers Jupiter, and result from the superposition of multiple physical processes which are difficult to disentangle. The goal of the proposed research is to complement observations using a process-oriented idealized experimental study of zonal jets emergence and equilibration.

Zonal jets are accelerated by Rossby waves when these waves dissipate and deposit their momentum, but jets also modify the propagation of the waves. This feedback effect can lead to a rich quasi-linear dynamics, in particular when multiple wave-driven jets are present. The goal of the proposed project is to use a wave-mean flow interaction approach to better understand what factors control the final equilibrium width of Jupiter’s jets, which is still a debated question despite centuries of observations. The successful candidate will use fluid mechanics experiments where we will directly force Rossby waves in a rotating water tank, study how they exchange energy with zonal jets, and characterize the long-term collective behaviour of multiple jets. The experimental set-up will be built in the state-of-the-art aquarium facility at the Scottish Oceans Institute in St Andrews. This work aims to obtain generic conclusions applicable to oceans and atmospheres in general, or to any rotating flow subject to topographic effects.

The successful candidate will join an exciting emerging team led by Dr Daphné Lemasquerier as part of her FLF project, alongside two postdoctoral fellows and two additional PhD students being hired over the duration of the project. This fellowship will provide the successful applicant with all the material resources necessary for the success of the project, and budget is available for international travel to attend conferences and summer schools. There are opportunities to teach in the School but teaching is not required.

The PhD student will more broadly become part of the Vortex Dynamics (Fluid Dynamics) group. It is one of three research groups in the Applied Mathematics Division of the School of Mathematics and Statistics, besides Solar and Magnetospheric Theory and Mathematical Biology. The group has 6 permanent members of academic staff with world-leading expertise in geophysical fluid dynamics, ranging from the banded circulation patterns and coherent vortices occurring in planetary atmospheres, to the ocean circulation, to oceanic vortex and current interactions, to geophysical turbulence, to cloud convection, to exact coherent structures in turbulent flows, to the melting/freezing of sea ice and to the flow of partially molten rock.

Both the Vortex Dynamics and the Applied Mathematics Division run research seminar programmes during semester to help students develop a broad knowledge beyond their PhD subject. The successful candidate will additionally meet informally with Dr Lemasquerier and the FLF team. These meetings aim to keep all members of the team informed about ongoing project and help tackle technical and intellectual challenges collectively.

The minimum academic entry requirement is a UK upper second class honours degree (or equivalent) in Applied Mathematics, Physics, Fluid Dynamics, Geo/Astrophysics or a closely related subject. Being fluent in both spoken and written English is essential (see the English language requirements). Apart from excellent academic qualifications, we expect applicants to have the self-motivation and enthusiasm to work on an interdisciplinary research project, at the intersection between fluid dynamics and planetary science.

The School of Mathematics and Statistics at the University of St Andrews values diversity and nurtures an inclusive community where everyone is treated with dignity and respect regardless of individual characteristics such as age, gender, disability, religion or ethnicity. It is firmly committed to the progression of women and other historically under-represented groups in mathematics and holds a Silver Award of the Athena SWAN programme for women in science. A growing proportion of our Ph.D. students are women, currently approximately 40%. The school supports the principles of the London Mathematical Society Good Practice Scheme.

Information about the PhD programme and application process, including eligibility criteria and how to apply, can be found at https://www.st-andrews.ac.uk/mathematics-statistics/prospective/pgr/. We strongly encourage all interested candidates to make their interest known as soon as possible by contacting Dr Daphné Lemasquerier (d.lemasquerier@st-andrews.ac.uk) to discuss the project.

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