Radiative Dynamics and Instabilities in Strongly Magnetized Relativistic Plasmas

Radiative Dynamics and Instabilities in Strongly Magnetized Relativistic Plasmas Relativistic plasmas in strong electromagnetic fields exhibit distinct dynamics compared to classical plasmas, with radiative and quantum electrodynamical (QED) effects fundamentally altering their collective properties and dynamics. Here, we investigate strongly magnetized plasmas for which synchrotron cooling timescales are comparable to the collective dynamical timescales, causing particles to radiate their energy, and surprisingly part of their collective entropy. This radiative cooling drives the plasma out of kinetic equilibrium, triggering kinetic instabilities. Our theory and simulations show that strongly magnetized plasmas spontaneously generate coherent, linearly polarized radiation through the interplay between radiative cooling and the electron cyclotron maser instability. These findings showcase the unique dynamics that radiative mechanisms introduce in relativistic plasmas, offering key insights into environments with intense electromagnetic fields such as neutron stars and magnetars. With laboratory experiments now able to recreate these conditions, we propose potential experimental platforms to probe these dynamics and link theory with astrophysical observations.