Large-amplitude low-frequency electromagnetic waves in pulsar magnetospheres

Abstract

Nonlinear propagation of strong low-frequency waves, as emitted by pulsars or compact galactic nuclei at their rotation frequencies, in a magnetized plasma is investigated. It is shown that even rather small amplitude waves can drive electrons to ultrarelativistic energies. In the limit when the electrons are ultrarelativistic but the ions are immobile, two types of circularly polarized waves (i.e., ω^± modes) are excited. In the wave zone of the Crab pulsar, both the electric field (∼ 3 V m⁻¹) and the wavelength (∼10⁸ m) of the ω^- mode are larger, by an order of magnitude, than those of the ω⁺ wave mode. Both ω^± modes can become modulationally unstable due to their nonlinear interaction with density fluctuations induced by the electrostatic waves.