Research

Astrophysical plasmas are extraordinary particle accelerators, capable of reaching efficiencies and particle energies far beyond what facilities can achieve on Earth. To understand the importance of fundamental processes at play—such as collisionless shocks, magnetic reconnection, and turbulence— progress relies on the tight interplay between theory, numerical modeling, and laboratory experiments. On the theoretical and computational side, models and large-scale simulations allow us to probe the microphysics and explore a wide range of astrophysical scenarios. At the same time, advances in high-power lasers make it possible to reproduce key plasma conditions in the laboratory. These controlled experiments provide a unique opportunity to test theoretical predictions and benchmark simulation codes, while also serving as a powerful complement to astronomical observations and spacecraft measurements.
Together, these approaches will allow us to address central questions: How do micro-instabilities regulate the injection of nonthermal particles? What mechanisms dominate particle acceleration? What sets the maximum attainable energy? 

Shock waves in plasmas are fascinating structures, playing a key role in both laboratory experiments and astrophysical environments. Early studies showed that a plasma shock is not a simple discontinuity, but rather a layered structure where electrons and ions behave differently before eventually reaching equilibrium. Later research revealed even richer dynamics: fast ions can stream ahead of the shock, creating instabilities and heating the plasma in unexpected ways. These effects blur the shock front and make its structure more complex than traditional fluid models predict. 

Today, many open questions remain, especially in the regime of weakly collisional shocks — a situation common in space and astrophysical plasmas, e.g., in galaxy clusters. This project combines theory, advanced simulations (with the codes SMILEI, PHARE, and FLASH), and cutting-edge laser experiments at the LULI2000 and GEKKO XII facilities. Together, these approaches will allow us to explore how shocks form and evolve, how they transition between collisional and collisionless states, and how they generate energetic particles and instabilities.

Cosmic rays, the most energetic particles in the Universe, can profoundly alter the plasmas they travel through. Near shock waves, they trigger powerful instabilities that amplify magnetic fields, drive wave activity, and heat the surrounding medium. Among these, the Weibel instability often dominates the earliest stages of shock formation in weakly magnetized environments. At later times, as the plasma evolves under the conditions shaped by the early Weibel phase, other instabilities such as the Bell and Firehose instabilities can take over, driving further magnetic field amplification and turbulence. However, the way these instabilities interact and influence one another over time remains largely unknown, making it one of the key open questions in plasma astrophysics.
Fully kinetic simulations using the full-PIC code SMILEI and the hybrid-PIC code PHARE are the key tools to capture the complex behaviour of electrons and ions, though they are computationally very demanding. Developing theoretical models alongside these simulations is a central goal of the project, helping to interpret results, guide the simulations, and provide predictive insight into the interplay between instabilities. By integrating these approaches, this work will clarify how cosmic rays drive turbulence and magnetic field amplification, advancing both astrophysical theory and laboratory plasma physics.

Ultra-intense magnetic fields in the Universe are the key to understanding the physics behind extreme scenarios such as pulsars, magnetars, and black holes. Our understanding is now shaped by astrophysical observations of the radiation spectrum, which indirectly characterize high-energy particle dynamics. A promising new approach is to reproduce ultra-strong magnetic fields in the laboratory, where they can be studied under controlled conditions.
Conventional technologies have reached their limits at around 100 teslas, but high-intensity lasers may allow us to push far beyond this threshold. When such lasers interact with plasma, they can generate powerful currents—and with them, intense magnetic fields—especially if the laser carries angular momentum. Circularly polarized beams or Laguerre–Gauss beams are particularly well suited, yet the details of how angular momentum is transferred to plasma particles are still not fully understood.
State-of-the-art kinetic simulations with the SMILEI code will enable us to explore how laser properties and plasma conditions affect the outcome. In synergy with the expertise of the experimental team at LULI, this research will shed new light on the physics of ultra-strong magnetic fields and guide future experimental platforms designed to probe astrophysical processes in the lab.