PhD proposal 2024

PhD thesis in astrophysical and laboratory plasma physics

The Interplay Between Cosmic Ray-Driven and Weibel Instabilities in Astrophysical and Laboratory Plasmas

Supervisors:

Andrea Ciardi

LERMA, Sorbonne University and Paris Observatory

Anna Grassi

 LULI, Sorbonne University and Ecole Polytechnique

Roch Smets

LPP, Sorbonne University and Ecole Polytechnique

Context. Cosmic rays are the source of a variety of instabilities in astrophysical plasmas, in particular in the vicinity of shocks, that lead to the non-linear growth of magnetic fluctuations, enhanced wave activity, and heating. In this thesis, the student will investigate the intricate interplay between cosmic ray-driven instabilities and other plasma micro-instabilities, with a particular focus on the Weibel instability, which can be the first and dominant instability during the shock formation stage in weakly magnetised environments. In addition to astrophysical plasmas, recent technological advances have now made it possible to study these instabilities in the laboratory, and in the context of high-energy density laboratory astrophysics. We are currently working on the design of the first experimental platform to study the non-resonant streaming instability, and its interplay with Weibel instability, using high-power lasers. Experimental results can provide stringent constraints on the model developed during the thesis as well as validation for the numerical tools employed.

Aims and Method. The student will work on theoretical models, numerical simulations, and the analysis of laboratory data to understand the impact of these instabilities on cosmic ray propagation and magnetic field amplification around shocks. By integrating these methodologies, the study aims to provide a broader understanding of the underlying mechanisms governing instability dynamics, energy transfer processes, and magnetic field evolution in space environments, thereby contributing to the broader field of plasma astrophysics and cosmic ray physics. 

The student will investigate the non-linear plasma evolution (heating, acceleration, filamentation...) under the influence of these instabilities using state-of-the-art numerical simulations with the full-PIC code SMILEI and the hybrid-PIC code PHARE. For the experimental plasmas, to model the initial plasma formation, additional simulations will be performed using our 3D resistive MHD code GORGON, which includes laser-matter interaction and PIC particles. The student will also work on improving these numerical tools.

Collaboration. The doctoral research is part of an international collaboration involving the LERMA, LULI, and LPP laboratories, Alexis Marret from the SLAC National Accelerator Laboratory, and Osaka University. The candidate will conduct research at Sorbonne Université, located on the Pierre and Marie Campus.