Intra-pulse variability induced by plasmoid formation in pulsar magnetospheres

• Main Authors: Andaç, I. Ceyhun, Cerutti, Benoît, Dubus, Guillaume, Ekşi, K. Yavuz
• Format: Journal Article
• Language: English
• Published: 04-05-2022
• Subjects: Physics - High Energy Astrophysical Phenomena; Physics - Plasma Physics
• DOI: 10.48550/arxiv.2205.01942

A&A 661, A130 (2022) Pulsars show irregularities in their pulsed radio emission that originate
from propagation effects and the intrinsic activity of the source. In this
work, we investigate the role played by magnetic reconnection and the formation
of plasmoids in the pulsar wind current sheet as a possible source of intrinsic
pulse-to-pulse variability in the incoherent, high-energy emission pattern. We
used a two-dimensional particle-in-cell simulation of an orthogonal pulsar
magnetosphere restricted to the plane perpendicular to the star spin axis. We
evolved the solution for several tens of pulsar periods to gather a
statistically significant sample of synthetic pulse profiles. The formation of
plasmoids leads to strong pulse-to-pulse variability in the form of multiple
short, bright subpulses, which appear only on the leading edge of each main
pulse. These secondary peaks of emission are dominated by the dozen plasmoids
that can grow up to macroscopic scales. They emerge from the high end of the
hierarchical merging process occurring along the wind current layer. The flux
of the subpulses is correlated with their width in phase. Although the
full-scale separation is not realistic, we argue that the simulation correctly
captures the demographics and the properties of the largest plasmoids, and
therefore of the brightest subpulses. The prediction of subpulses at specific
pulse phases provides a new observational test of the magnetic reconnection
scenario as the origin of the pulsed incoherent emission. High-time-resolution
observations of the Crab pulsar in the optical range may be the most promising
source to target for this purpose.