PhD Studentship - Nonlinear ALFVEN Waves in High Magnetic Field

Description of thesis topic

Turbulence in magnetic fields, or magnetohydrodynamic turbulence, is a fundamental process that underpins our understanding of a variety of natural and industrial processes:  heat in the outer solar envelope (solar Corona), how the Earth sustains its magnetic field, but also how to obtain defect free metallic alloys. The Lorentz force affects turbulence via two processes, a diffusive process that tends to make the flow two-dimensional and wave propagation expressing as a family of “Alfven” waves travelling along magnetic field lines.

Competition and interaction between these processes is not well understood because Alfven waves can only be investigated at laboratory scale in a very high magnetic field environment. As a consequence, experimental data on Alfvenic turbulence is limited to astrophysical observations, and studies concerning turbulence have focused on engineering processes and assuming that the Lorentz force is exclusively diffusive. In the past year our team has challenged this paradigm by experimentally producing Alfven waves backed by a new theory, and so opened the way for a laboratory experiments on propagative MHD turbulence hitherto thought impossible.

The PhD student will carry out experiments on Alfven waves and turbulence, in the world-unique high magnetic field environment available at LNCMI-Grenoble that made these experiments possible. The joint experimental/numerical approach developed during the PhD will be based on the FLOWCUBE platform developed to study asymptotic MHD flows in the turbulent regime as well as to electrically excite Alfven (torsional) waves.  

High magnetic fields (up to 17 T in a bore 376 mm in diameter) will be used to perform the experiments. The PhD student will adapt the FLOWCUBE experiment to investigate nonlinear interaction of Alfven waves as well as the coupling between Alfven Waves and a background flow, either laminar or turbulent. Dual-frequency modulation of injected electric currents will be used to drive steady flows and Alfven wave interactions and to investigate the spectral behavior of MHD turbulence modified by wave propagation and interaction under high magnetic field conditions. 

The starting date of the PhD is expected to be Autumn 2024.

The experiments will be split into 3 campaigns of measurements during the first 30 months of the PhD.

The PhD will be actively involved in planning these campaigns as it depends critically on the acceptation of the proposed experimental session by the “selection committee” of the EMFL consortium.

The PhD student will develop the physical model on nonlinear interaction of Alfven waves, extending in this way the recent work produced by Samy Lalloz during his PhD supported by a previous research  programme between 2020 and 2023.

Work Context

This cotutelle PhD thesis will take place at the LNCMI laboratory (UPR 3228 CNRS) in Grenoble and at Coventry university in the UK. It will be co-supervised by Prof. Laurent Davoust, Simap Laboratory Grenoble, Prof. Alban Potherat, Coventry University and by Dr. François Debray, LNCMI Grenoble.

Period of works in Coventry will be organized during the PhD.

Additional Information

The candidate should hold a Master’s degree in Applied or Theoretical Physics or Fluid Mechanics, with a particular interest in experimental investigation and data processing. A good command of English is essential with a view to making oral presentations at international conferences and writing international articles.

To apply, please contact directly either Prof. Potherat (alban.potherat@coventry.ac.uk), Prof Davoust (laurent.davoust@grenoble-inp.fr) or Dr. Debray (francois.debray@lncmi.cnrs.fr)

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