Fast Radio Bursts produced during collapse of macroscopic X-mode in magnetized pair plasma

Abstract

We demonstrate that in highly magnetized pair plasma nonlinear long-wavelength X-modes experience wave collapse/breaking, whereby the wave undergoes severe spatial steepening, driven by nonlinear modifications of the refractive index and strong ponderomotive forces. The collapse/wave breaking occurs in a narrow parameter regime, when the fluctuating part of the magnetic field exceed the guide field, and plasma magnetization is close to the current starvation regime. This regime is naturally achieved in highly magnetized neutron stars, magnetars. Breaking during a fraction of the dynamic timescale, and quickly generates high-k modes. The initial EM energy, spread over large spatial scales, is squeezed into these highly localized, short-wavelength (yet macroscopic) singular pulses. The corresponding electromagnetic ``foam'' spectrum is red, $E_k \propto k^{-2}$, while the particles' spectrum is exceptionally hard, $f(γ) \propto γ^0$ The wave collapse produces short bright EM pulses - astrophysical Fast Radio Bursts. The highest energy particles may produce short contemporaneous high energy bursts.