Revealing cosmic magnetism in the near future: promises and challenges of Faraday rotation

The last decade marked a breakthrough in the study of cosmic magnetism, from our Galaxy to the large-scale structure of the Universe. The unprecedented amount and quality of polarization data from the radio to the infrared bands started shedding light on the tight coupling between magnetic fields and interstellar matter. A new observational window is now open to understand the role of magnetic fields in the dynamical evolution of galaxies and star formation. Despite the unfortunate faith of next-generation infrared space missions, the growing development of ground-based interferometric facilities at low radio frequencies, such as LOFAR, NenuFAR, and the Square Kilometer Array with its precursors, and their interface with higher-frequency instruments, like ALMA and IRAM-NIKA2, will continue to unveil the complex relationship between matter and magnetization in the interstellar medium. In this workshop we propose to explore and discuss some of the promises and challenges that will be faced by polarimetric observations of synchrotron radiation at low radio frequencies and highlight the potential of Faraday rotation as a tool to measure magnetic fields in the multiphase interstellar gas across cosmic scales. In particular, the ability to master the complexity of present and future radio polarimetric observations will depend on our understanding of fundamental problems, from an accurate description of cosmic-ray propagation to the evolution of the ionization state across gas phases in the dynamical interstellar medium. The workshop will be held at Ecole Normale Supérieure (LPENS, 24 rue Lhomond, Paris) on December 5-6 2022.