Mimic astrophysical cosmic-ray sources with lab plasmas

• Applicant: Dr. Patrick Reichherzer
• Subject Area: Astrophysics and Astronomy
• Term: since 2023
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 518672034

High-energy particles constantly bombard Earth. Charged, relativistic particles, referred to as cosmic rays (CRs), are deflected on their way through the magnetised Universe towards Earth. This characteristic of CRs obscures their origin to this day. The importance of CRs in astrophysical systems of all sizes is known in great detail, from planetary systems up to the interstellar medium and even galaxy clusters. On Earth, we can observe the influence of CRs through polar lights. Here, CRs ionise and excite the atmospheric constituents that emit visible light.Despite decades of research on analytical theories, numerical simulations and indirect observations, we still haven't unravelled the mystery of the CR's origin. To make further progress, the Oxford group I'll be working with recently mimicked the transport of CRs through the intergalactic medium in a laboratory experiment (Chen et al. 2020) for the first time. They used powerful laser systems, among them the most energetic laser in the world, capable of bringing the powerful dynamics of the Universe to the laboratory. This was a milestone in establishing laboratory physics as a new pillar alongside analytical theories, numerical simulations and observations.The key objective of this study is to investigate the signatures of the interplay between magnetised, turbulent plasmas and CRs in their potential sources by studying dedicated laboratory experiments that extend our current understanding shaped through analytical theories and numerical simulations. In the proposed project, I will move on with charged particles subject to stronger magnetic field strength with an additional ordered component. This novel setup mimics the transport of CRs in their potential astrophysical sources and delivers a statistical description of transport characteristics governed by the diffusion tensor dependencies. I will feed these statistical properties into numerical astrophysical simulations employing efficient statistical methods. Modelling the generation of multimessenger signals through the interaction of CRs with target photons and matter, as well as magnetic fields, allows verification through observations. Joining the exceptional environment amidst expertise in plasma-, lab-, astroparticle- and astrophysics present in the research landscape of Oxford is necessary to achieve the objectives of this interdisciplinary proposal. By combining my experience with theoretical and numerical endeavours of CR transport and source physics with the unprecedented possibilities of lab experiments, I will synergise their interplay in the world-leading research environment of Oxford to tackle the fundamental question of the CR origin decisively.

• DFG Programme: WBP Fellowship
• International Connection: United Kingdom
• Host: Professor Dr. Gianluca Gregori