Missions

The properties of wave propagation in a moving medium differ from those in a medium at rest. In the case of a rotating medium, rotation leads to circular birefringence, and thus to a rotation of the polarization of a linearly polarized wave propagating along the rotation axis of this medium (left hand-side figure below). In plasmas, it has recently been uncovered that this mechanical effect might be at play in the rotating magnetosphere that surrounds pulsars, possibly affecting galactic magnetic field measurements in astrophysics [1]. This same mechanical effect in plasmas may also enable new means to manipulate light in laboratory on Earth [2]. Furthermore, beyond affecting wave polarization, that is the spin component of the wave's angular momentum, it has just been found that plasma rotation can also affect the wave's orbital angular momentum in a phenomenon known as image rotation [3] (right hand-side figure below). This is the manifestation of the beam drag induced by the medium's motion. Besides bringing forth a suite of fundamental questions [4], this new effect in plasmas may hold promise for rotation diagnostics, notably in magnetic confinement fusion experiments.
[1] R. Gueroult et al. (2019), Nat. Commun., 10, 3232
[2] R. Gueroult, J.-M. Rax and N. J. Fisch (2020), Phys. Rev. E, 102, 051202(R)
[3] J.-M. Rax and R. Gueroult (2021), J. Plasma Phys., 87, 905870507
[4] R. Gueroult, J.-M. Rax and J. J. Fisch (2023), Plasma Phys. Control. Fusion, 65, 34006

Activités

Despite these new results, the effect of motion on plasma waves remains largely
unexplored, and also importantly unaccounted for in models. The more systematic study of these effects is the objective of the ANR-funded Warp project which started in 2022, in collaboration with specialists both in astrophysics and high-energy density plasma experiments. This includes two PhD theses, currently working on developing models to capture the effect of rotation on plasma waves [5,6], beyond the simple models available to date. An objective of the Warp project is however to eventually used these models to assess the importance of these effects in experiments or natural environments. The proposed scope for this postdoctoral project is therefore to apply these new models to practical rotating plasma configurations, to quantify the importance of rotation effects in these environments. This could, for instance and depending on the candidate's skills and interests, be in astrophysics or magnetic confinement fusion. Ultimately the goal will be to propose ways to account for or leverage these effects.
[5] J. Langlois and R. Gueroult (2023), Phys. Rev. E, 108, 045201
[6] J. Langlois and R. Gueroult (2024), arXiv:2402.12050

Compétences

Strong analytical skills, good physical intuition, curiosity and resourcefulness are
essential assets for this project. Knowledge of and experience with wave physics in the context of magnetic confinement fusion and/or space physics will be helpful.
Keywords - Electrodynamics / electromagnetism & optics / plasma physics.

Contexte de travail

This position is funded by the ANR WaRP research project for “Waves in Rotating Plasmas”. This 54-month project began in March 2022, and focuses on the study of the effect of rotation on wave propagation in plasmas. This postdoctoral position is for 18 months.
The Laplace (Plasma and Energy Conversion Laboratory) is a joint research unit supervised by CNRS, INP-Toulouse and UPS. The laboratory has a staff of over 300 and represents the largest concentration of research in electrical engineering and plasma in France.

Le poste se situe dans un secteur relevant de la protection du potentiel scientifique et technique (PPST), et nécessite donc, conformément à la réglementation, que votre arrivée soit autorisée par l'autorité compétente du MESR.