Kinetic model of large-amplitude oscillations in neutron star pair cascades

TL;DR

This paper presents an analytical and numerical study of large-amplitude oscillations in neutron star pair cascades, revealing plasma instabilities and secondary pair bursts driven by electromagnetic field interactions.

Contribution

It introduces a simplified kinetic model linking QED pair production processes to plasma oscillations and validates it with particle-in-cell simulations.

Findings

Large-amplitude oscillations are driven by plasma instabilities.

Secondary pair bursts damp oscillations.

Analytical model agrees with simulations.

Abstract

Electron-positron pair cascades developed in the extreme electromagnetic fields of neutron star polar caps are considered a key source of magnetospheric plasma in these objects. We use a simplified model that maps the Quantum Electrodynamics processes governing the pair cascades to analytically and numerically model the development of the pair cascade, and show that large-amplitude oscillations of the electric field are inductively driven by the resulting plasma. A plasma instability arises in these oscillations, and particles accelerated in growing electric field perturbations can drive secondary pair bursts that damp the large-amplitude oscillations. An analytical model is proposed to describe this interplay between the pair production and kinetic collective plasma processes. All analytical results are shown to be in excellent agreement with particle-in-cell simulations.