Scattering of Ultrastrong Electromagnetic Waves by Magnetized Particles

Observations of powerful radio waves from neutron star magnetospheres raise the question of how strong waves interact with particles in a strong background magnetic field B_{bg}. This problem is examined by solving the particle motion in the wave. Remarkably, waves with amplitudes E_{0}>B_{bg} pump particle energy via repeating resonance events, quickly reaching the radiation reaction limit. As a result, the wave is scattered with a huge cross section. This fact has implications for models of fast radio bursts and magnetars. Particles accelerated in the wave emit γ rays, which can trigger an e^{±} avalanche and, instead of silent escape, the wave will produce x-ray fireworks.