The PhD will primarily be based at the LULI site located at École Polytechnique (Palaiseau). A part of the thesis will involve conducting experimental campaigns on the LULI2000 laser located at the same site. LULI2000 is an international high-energy laser facility; an experimental campaign related to this thesis topic has already been accepted and scheduled for mid-2025. Another part of the thesis will be dedicated to numerical simulations. A computing allocation on a supercomputer has been specifically assigned for this project.

This thesis is part of funding awarded to a consortium bringing together four research teams: at LULI and CEA-DIF for laser-plasma interaction, at LPP (Laboratory of Plasma Physics) for the theoretical and numerical aspects of space plasmas, and at the Paris Observatory for observations related to solar emissions. The PhD student will benefit from this multidisciplinary collaboration.

Solar burst study in the laboratory by laser-plasma interaction.

The sun is a place of intense activity that leads to violent phenomena such as solar flares or particle acceleration. This thesis specifically focuses on solar bursts: intense radio emissions (detected by ground-based or spatial telescopes) arising from various types of solar activity. These emissions can sometimes be intense enough to disrupt or damage satellites or terrestrial electrical systems. Generally, these solar bursts are induced by electron beams propagating through the sun's atmosphere. Thus, studying the characteristics of radio emissions can provide information about the mechanisms of electron acceleration and the plasma conditions they traverse.

During their propagation, these energetic electrons excite Langmuir waves (LW) in the plasma. The decay and coupling of these primary LWs generate electromagnetic (EM) waves at the plasma frequency ωp or its first harmonic 2ωp, which are detected by telescopes in the radiowave domain. Several mechanisms can be responsible for the conversion of LWs into EM radiation, theoretically leading to different signatures in their emission diagram, their polarization, and the intensity ratio between ωp and 2ωp emissions.

Our team demonstrated, through experiments on the high-energy laser LULI2000, that the same electromagnetic radiation at ωp and 2ωp can be reproduced by laser-plasma interaction. The principle of these experiments is to replace the electron beam with a laser: instead of generating LWs via an electron beam, LWs are produced by Raman instability.

In the solar scenario, the polarization of these emissions at ωp and 2ωp does not always follow theoretical predictions, possibly due to a complex magnetic field configuration. To experimentally establish the effect of a magnetic field on these EM emissions, we propose as a thesis topic to study in the laboratory (specifically on the LULI2000 laser) their generation and characteristics in the presence of an external static magnetic field. The experimental study will be complemented by the realization and analysis of numerical simulations using a plasma simulation code irradiated by laser.

The most relevant knowledge includes plasma physics, classical electrodynamics, and optics. Basic knowledge in space physics and numerical physics is also appreciated. The application should include a detailed CV, the email address of two academics who can provide a reference letter, a one-page motivation letter, and the Master 1 and 2 grades.