PhD M/F - Energy Transfer in Turbulent Space Plasmas

Job Description

Thesis Subject

Scientific context and hypothesis:

Approximately 99% of the visible Universe is made of plasma, an ionized gas of charged particles corresponding to the “fourth state” of matter. Plasmas are ubiquitous in nature, from the solar corona and solar wind to planetary magnetospheres and stellar systems. They are also at the core of several strategic technologies, such as nuclear fusion and cutting-edge medical devices. Despite the diversity of the environments in which they exist or are created, plasmas share a fundamental property: their dynamics are strongly nonlinear and characterised by interactions over a broad range of spatial and temporal scales.

In particular, space plasmas are highly turbulent systems in which energy is continuously injected, transferred through nonlinear interactions between the different scales involved in their dynamics, and eventually dissipated. At the smallest scales, kinetic effects become increasingly important, and the energy ultimately contributes to plasma heating and is transferred to ions and electrons through various mechanisms, including magnetic reconnection and wave-particle interactions. Energy exchanges among kinetic, magnetic and thermal components also play an important role in the dynamics of turbulent plasmas.

Characterising energy transfer in space plasmas, from the sources of energy, through the direction of the energy cascade, to dissipation, remains a fundamental open problem in plasma physics. In particular, the connection between turbulent cascades at magnetohydrodynamic (MHD) scales and the phenomena responsible for energy transfer and dissipation at kinetic scales is only partially understood. Given the complexity of this highly nonlinear framework, a comprehensive characterisation of how energy is redistributed across the vast dynamical range of scales, from the scales characteristic of solar and heliospheric phenomena down to ion and electron scales, as well as the investigation of direct and inverse energy transfers in space plasmas, requires a thorough assessment of energy fluxes, quadratic quantities based on velocity and magnetic fields, and the analysis of plasma-wave propagation. This can be enabled by combining state-of-the-art spacecraft observations, high-resolution numerical simulations and theoretical modelling.
Objectives:

The main objective of this PhD is to quantitatively characterise energy transfer in space plasmas using datasets from single- and multi-spacecraft missions, high-performance computing and advanced theoretical approaches, in order to investigate the evolution of turbulence in the solar wind and planetary environments, such as the Earth's magnetosphere, and its interplay with the propagation of plasma waves. The project will focus on the investigation of the spectral and statistical properties of turbulence, intermittency, and the signatures of coherent structures, magnetic reconnection and wave propagation. Using high-resolution numerical simulations, the relevant physical mechanisms identified through the analysis of spacecraft observations will be studied over a range of parameters of direct relevance to solar-wind and magnetospheric plasmas. In particular, the energy flow from the MHD range to regimes in which kinetic effects become important will be investigated, as well as the main mechanisms responsible for energy dissipation and energy conversion at ion and electron scales.
Methodology:

The project will combine spacecraft-data analysis, high-resolution numerical simulations and theoretical modelling. Spacecraft datasets will be used to characterise fluctuations of the magnetic, velocity and other relevant fields, as well as the evolution of the probability distribution functions of different plasma species. Observations from European Space Agency (ESA) missions, in particular Solar Orbiter, as well as from JAXA and NASA missions, will be analysed within the project. Preparatory research in support of future missions, such as Plasma Observatory and HelioSwarm, will also be carried out.

Depending on the physical regime considered, several numerical approaches may be employed, including pseudo-spectral, lattice-Boltzmann and kinetic Vlasov simulations. These will make it possible to explore a range of parameters directly relevant to heliospheric and magnetospheric plasmas and to characterise the mechanisms investigated through spacecraft observations.

The tools developed within the project will be used to assess inter-scale energy transfers, energy exchanges among kinetic, magnetic and thermal components, and statistical properties of plasma fields in space. Machine-learning techniques will be implemented for the analysis of large observational and numerical datasets, in synergy with classical statistical analyses and novel mathematical methodologies.
Impact:

This work will provide new insight into the mechanisms governing energy transfer and dissipation in turbulent space plasmas. In the longer term, the results will contribute to improving models for the evolution of solar and heliospheric plasmas and therefore help improve the quality of space-weather predictions and support the preparation of future space missions, in particular the ESA Plasma Observatory mission, through the development of tools for analysing large observational datasets.

Achieving a better understanding of how energy is transferred and how different types of instabilities develop in turbulent plasmas is also of broader relevance to plasma physics and technological applications, including fusion plasmas. Characterising turbulent transport and nonlinear interactions between structures at different scales are indeed common challenges in astrophysical and laboratory plasmas. The results obtained in this project may therefore contribute to strengthening links between the communities working on astrophysical, fusion and fundamental plasmas.

Your Work Environment

This PhD project is part of a French-Japanese collaboration between the CNRS and the University of Tokyo, bringing together expertise in turbulent plasma physics, numerical and theoretical plasma modelling, and spacecraft-data analysis. The project will also benefit from collaborations with institutions in France and other European countries involved in turbulence and space plasma research and in ESA missions, in particular Solar Orbiter and Plasma Observatory.

The PhD student will be based at École Centrale de Lyon, conducting research under the supervision of Dr. Raffaele Marino within the Laboratoire de Mécanique des Fluides et d'Acoustique, where they will benefit from an interdisciplinary research environment at the interface of plasma physics, fluid mechanics, high-performance computing and experimental data analysis. The PhD project has dedicated funding for research visits to Japan, which will allow the PhD student to work directly with partners at the University of Tokyo and benefit from their expertise. Research visits to other European institutions are also envisaged as part of the PhD project's scientific collaborations.

Constraints and risks

Constraints: The position will be based at École Centrale de Lyon and will involve research visits to Japan. Visits to European partner institutions may also be envisaged. The project will require the use of computational resources and the analysis of large volumes of spacecraft data.

Risks: The project does not involve specific experimental, biological or chemical risks. The main points of attention are related to the intensive use of high-performance computing infrastructures and international travel.

Compensation and benefits

Compensation

2300 € gross monthly

Annual leave and RTT

44 jours

Remote Working practice and compensation

Pratique et indemnisation du TT

Transport

Prise en charge à 75% du coût et forfait mobilité durable jusqu’à 300€

About the offer

About the CNRS

The CNRS is a major player in fundamental research on a global scale. The CNRS is the only French organization active in all scientific fields. Its unique position as a multi-specialist allows it to bring together different disciplines to address the most important challenges of the contemporary world, in connection with the actors of change.

CNRS

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