Tracking the complete evolution of electromagnetic instability in an ultra-intense laser-driven plasma

Plasmas, the most common state of matter in the observable universe, are subject to instabilities of various types: hydrodynamic, magnetohydrodynamic, and electromagnetic. Our limited success in understanding these is due to the lack of direct experimental information on their origins and evolution. Here, we present direct spatially resolved measurements of the femtosecond evolution of the electromagnetic beam-driven instability that arises from the interaction of forward and return currents in an ultrahigh-intensity laser-produced plasma. We track its evolution from the initial linear stage to the later nonlinear stage by measuring the spatiotemporal evolution of the giant (megagauss) magnetic field created in the interaction process. Our experimental findings and numerical simulations are the first to indicate the observed instability triggered by the emission of electromagnetic radiation, like those known in the context of gravitational interaction, where the emission of gravitational radiation drives specific negative-energy modes in rotating black holes or neutron stars.